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add more easy problem solutions
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‎algorithms/374-guess-number-higher-or-lower.ipynb

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "visible-publisher",
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"metadata": {},
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"source": [
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"### [猜数字大小](https://leetcode-cn.com/problems/guess-number-higher-or-lower/)\n",
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"\n",
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"猜数字游戏的规则如下：\n",
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"\n",
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"- 每轮游戏，我都会从 1 到 n 随机选择一个数字。 请你猜选出的是哪个数字。\n",
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"- 如果你猜错了，我会告诉你，你猜测的数字比我选出的数字是大了还是小了。\n",
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"\n",
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"你可以通过调用一个预先定义好的接口 int guess(int num) 来获取猜测结果，返回值一共有 3 种可能的情况（-1，1 或 0）：\n",
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"- -1：我选出的数字比你猜的数字小 pick < num\n",
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"- 1：我选出的数字比你猜的数字大 pick > num\n",
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"- 0：我选出的数字和你猜的数字一样。恭喜！你猜对了！pick == num\n",
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"\n",
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"返回我选出的数字。\n",
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"\n",
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"\n",
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"#### 示例 1：\n",
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"```\n",
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"输入：n = 10, pick = 6\n",
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"输出：6\n",
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"```\n",
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"\n",
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"#### 示例 2：\n",
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"```\n",
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"输入：n = 1, pick = 1\n",
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"输出：1\n",
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"```\n",
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"\n",
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"#### 示例 3：\n",
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"```\n",
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"输入：n = 2, pick = 1\n",
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"输出：1\n",
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"```\n",
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"\n",
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"#### 示例 4：\n",
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"```\n",
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"输入：n = 2, pick = 2\n",
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"输出：2\n",
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"```\n",
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"\n",
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"#### 提示：\n",
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"- $ 1 <= n <= 2^{31} - 1 $\n",
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"- $ 1 <= pick <= n $"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"id": "biological-spider",
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"metadata": {},
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"outputs": [],
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"source": [
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"# The guess API is already defined for you.\n",
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"# @param num, your guess\n",
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"# @return -1 if my number is lower, 1 if my number is higher, otherwise return 0\n",
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"# def guess(num: int) -> int:\n",
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"\n",
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"class Solution:\n",
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" def guessNumber(self, n: int) -> int:\n",
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" \n",
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" def binarySearch(l, r):\n",
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" if l > r:\n",
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" return -1\n",
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" \n",
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" mid = l + (r - l) // 2\n",
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" result = guess(mid)\n",
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" if result == 1:\n",
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" return binarySearch(mid + 1, r)\n",
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" elif result == -1:\n",
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" return binarySearch(l, mid - 1)\n",
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" else:\n",
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" return mid\n",
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" \n",
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" return binarySearch(1, n)"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.8.6"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

‎algorithms/387-first-unique-character-in-a-string.ipynb

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "photographic-mandate",
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"metadata": {},
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"source": [
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"### [字符串中的第一个唯一字符](https://leetcode-cn.com/problems/first-unique-character-in-a-string/)\n",
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"\n",
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"给定一个字符串，找到它的第一个不重复的字符，并返回它的索引。如果不存在，则返回 -1。\n",
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"\n",
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"#### 示例：\n",
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"```\n",
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"s = \"leetcode\"\n",
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"返回 0\n",
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"```\n",
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"```\n",
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"s = \"loveleetcode\"\n",
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"返回 2\n",
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"```\n",
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"\n",
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"提示：你可以假定该字符串只包含小写字母。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"id": "experienced-teaching",
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"metadata": {},
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"outputs": [],
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"source": [
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"from collections import Counter\n",
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"\n",
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"def firstUniqChar(s: str) -> int:\n",
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" counter = Counter(s)\n",
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" for i, c in enumerate(s):\n",
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" if counter[c] == 1:\n",
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" return i\n",
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" return -1"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"id": "soviet-optimization",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"2"
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]
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},
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"execution_count": 4,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"firstUniqChar(\"loveleetcode\")"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 5,
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"id": "dated-labor",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"0"
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]
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},
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"execution_count": 5,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"firstUniqChar(\"leetcode\")"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.8.6"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

‎algorithms/389-find-the-difference.ipynb

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "median-plaza",
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"metadata": {},
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"source": [
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"### [找不同](https://leetcode-cn.com/problems/find-the-difference/)\n",
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"\n",
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"给定两个字符串 s 和 t，它们只包含小写字母。\n",
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"\n",
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"字符串 t 由字符串 s 随机重排，然后在随机位置添加一个字母。\n",
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"\n",
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"请找出在 t 中被添加的字母。\n",
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"\n",
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"#### 示例 1：\n",
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"```\n",
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"输入：s = \"abcd\", t = \"abcde\"\n",
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"输出：\"e\"\n",
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"解释：'e' 是那个被添加的字母。\n",
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"```\n",
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"\n",
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"#### 示例 2：\n",
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"```\n",
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"输入：s = \"\", t = \"y\"\n",
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"输出：\"y\"\n",
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"```\n",
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"\n",
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"#### 示例 3：\n",
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"```\n",
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"输入：s = \"a\", t = \"aa\"\n",
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"输出：\"a\"\n",
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"```\n",
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"\n",
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"示例 4：\n",
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"```\n",
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"输入：s = \"ae\", t = \"aea\"\n",
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"输出：\"a\"\n",
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"```\n",
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"\n",
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"#### 提示：\n",
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"- 0 <= s.length <= 1000\n",
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"- t.length == s.length + 1\n",
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"- s 和 t 只包含小写字母"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"id": "connected-hughes",
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"metadata": {},
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"outputs": [],
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"source": [
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"from collections import Counter\n",
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"\n",
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"def findTheDifference(s: str, t: str) -> str:\n",
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" counter1, counter2 = Counter(s), Counter(t)\n",
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" for c, v1 in counter2.items():\n",
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" if c not in counter1:\n",
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" return c\n",
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" else:\n",
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" v2 = counter1[c]\n",
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" if v1 > v2:\n",
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" return c\n",
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" return None"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"id": "paperback-people",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"'a'"
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]
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},
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"execution_count": 3,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"findTheDifference(\"ae\", \"aea\")"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"id": "coordinated-nurse",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"'a'"
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]
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},
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"execution_count": 4,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"findTheDifference(\"a\", \"aa\")"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 5,
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"id": "excited-offering",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"'y'"
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]
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},
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"execution_count": 5,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"findTheDifference(\"\", \"y\")"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 6,
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"id": "caroline-collection",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"'e'"
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]
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},
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"execution_count": 6,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"findTheDifference(\"abcd\", \"abcde\")"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.8.6"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

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