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zhuli19901106zhuli19901106
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13 medium problems
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‎continuous-subarray-sum_1_AC.cpp

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#include <unordered_map>
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using std::unordered_map;
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class Solution {
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public:
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bool checkSubarraySum(vector<int>& nums, int k) {
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auto &a = nums;
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int n = a.size();
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int i;
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if (k == 0) {
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int cc;
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i = 0;
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while (i < n) {
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if (a[i] != 0) {
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++i;
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continue;
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}
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cc = 0;
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while (i < n && a[i] == 0) {
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++i;
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++cc;
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}
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if (cc >= 2) {
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return true;
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}
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}
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return false;
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}
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unordered_map<int, int> um;
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um[0] = 0;
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int sum = 0;
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for (i = 0; i < n; ++i) {
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sum = (sum + a[i]) % k;
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if (um.find(sum) == um.end()) {
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um[sum] = i + 1;
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}
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if (i + 1 - um[sum] >= 2) {
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break;
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}
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}
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um.clear();
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return i < n;
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}
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};

‎design-snake-game_1_AC.cpp

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// Edge cases everywhere.
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#include <string>
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#include <unordered_map>
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#include <vector>
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using std::string;
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using std::unordered_map;
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using std::vector;
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static const int offset[4][2] = {{-1, 0}, {+1, 0}, {0, -1}, {0, +1}};
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typedef struct MyListNode {
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int x, y;
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struct MyListNode *next;
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MyListNode(int _x = 0, int _y = 0): x(_x), y(_y), next(NULL) {}
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} MyListNode;
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class SnakeGame {
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public:
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/** Initialize your data structure here.
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@param width - screen width
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@param height - screen height
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@param food - A list of food positions
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E.g food = [[1,1], [1,0]] means the first food is positioned at [1,1], the second is at [1,0]. */
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SnakeGame(int width, int height, vector<pair<int, int>> food) {
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static const string sd = "UDLR";
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int ls = sd.size();
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int i;
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for (i = 0; i < ls; ++i) {
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di[sd[i]] = i;
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}
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n = height;
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m = width;
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int sx = 0;
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int sy = 0;
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head = tail = new MyListNode(sx, sy);
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f = food;
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fi = 0;
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if (fi < f.size()) {
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fx = f[fi].first;
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fy = f[fi].second;
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} else {
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fx = fy = -1;
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}
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b.resize(n, vector<bool>(m, false));
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b[sx][sy] = true;
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score = 0;
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}
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/** Moves the snake.
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@param direction - 'U' = Up, 'L' = Left, 'R' = Right, 'D' = Down
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@return The game's score after the move. Return -1 if game over.
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Game over when snake crosses the screen boundary or bites its body. */
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int move(string direction) {
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int i = di[direction[0]];
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int x, y;
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x = tail->x + offset[i][0];
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y = tail->y + offset[i][1];
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if (!inbound(x, y) || (b[x][y] && !(x == head->x && y == head->y))) {
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// Game over
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// An edge case here, watch out.
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return -1;
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}
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if (x == fx && y == fy) {
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// Eat something
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tail->next = new MyListNode(x, y);
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tail = tail->next;
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b[x][y] = true;
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++score;
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++fi;
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if (fi < f.size()) {
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fx = f[fi].first;
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fy = f[fi].second;
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} else {
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fx = fy = -1;
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}
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} else {
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b[head->x][head->y] = false;
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head->x = x;
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head->y = y;
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b[x][y] = true;
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if (head != tail) {
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MyListNode *p = head;
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head = p->next;
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p->next = NULL;
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tail->next = p;
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tail = p;
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}
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}
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return score;
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}
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~SnakeGame() {
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di.clear();
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b.clear();
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f.clear();
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MyListNode *p = head;
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while (head != NULL) {
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head = head->next;
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delete p;
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p = head;
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}
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}
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private:
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unordered_map<char, int> di;
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MyListNode *head, *tail;
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int n, m;
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int fx, fy;
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int fi;
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vector<vector<bool>> b;
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vector<pair<int, int>> f;
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int score;
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bool inbound(int x, int y) {
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return x >= 0 && x <= n - 1 && y >= 0 && y <= m - 1;
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}
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};
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/**
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* Your SnakeGame object will be instantiated and called as such:
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* SnakeGame obj = new SnakeGame(width, height, food);
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* int param_1 = obj.move(direction);
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*/

‎encode-and-decode-strings_1_AC.cpp

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// Base64 is an option.
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#include <cctype>
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#include <string>
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#include <vector>
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using std::isdigit;
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using std::string;
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using std::to_string;
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using std::vector;
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class Codec {
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public:
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Codec() {
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b64 = "";
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bi.resize(SIZE_DICT, -1);
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int idx = 0;
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int i;
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for (i = 0; i < 26; ++i) {
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b64.push_back('A' + i);
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bi['A' + i] = idx++;
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}
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for (i = 0; i < 26; ++i) {
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b64.push_back('a' + i);
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bi['a' + i] = idx++;
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}
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for (i = 0; i < 10; ++i) {
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b64.push_back('0' + i);
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bi['0' + i] = idx++;
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}
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b64.push_back('+');
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bi['+'] = idx++;
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b64.push_back('/');
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bi['/'] = idx++;
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}
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// Encodes a list of strings to a single string.
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string encode(vector<string>& strs) {
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auto &a = strs;
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int n = a.size();
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string res = "";
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res.push_back(CHAR_SEQ_DEL);
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for (auto &s: a) {
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res += encodeSingle(s);
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}
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res.push_back(CHAR_SEQ_DEL);
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return res;
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}
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string encodeSingle(string &s) {
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string t = encodeBase64(s);
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int lt = t.size();
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string res = "";
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res.push_back(CHAR_WORD_DEL);
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res += to_string(lt);
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res.push_back(CHAR_WORD_DEL);
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res += t;
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res.push_back(CHAR_WORD_DEL);
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return res;
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}
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// Decodes a single string to a list of strings.
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vector<string> decode(string s) {
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vector<string> res;
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int ls = s.size();
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if (!(ls >= 2 && s[0] == CHAR_SEQ_DEL && s[ls - 1] == CHAR_SEQ_DEL)) {
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return res;
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}
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int i, j;
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string ss;
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i = 1;
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while (i < ls - 1) {
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j = i + 1;
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while (j < ls - 1 && s[j] != CHAR_WORD_DEL) {
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++j;
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}
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++j;
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while (j < ls - 1 && s[j] != CHAR_WORD_DEL) {
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++j;
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}
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++j;
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ss = s.substr(i, j - i);
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res.push_back(decodeSingle(ss));
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i = j;
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}
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return res;
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}
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string decodeSingle(string &s) {
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string res = "";
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int ls = s.size();
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if (!(ls >= 2 && s[0] == CHAR_WORD_DEL && s[ls - 1] == CHAR_WORD_DEL)) {
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return res;
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}
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int i = 1;
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int lt = 0;
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while (i < ls && isdigit(s[i])) {
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lt = lt * 10 + (s[i] - '0');
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++i;
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}
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++i;
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string t = s.substr(i, ls - 1 - i);
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if (t.size() != lt) {
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return res;
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}
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return decodeBase64(t);
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}
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~Codec() {
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b64.clear();
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bi.clear();
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}
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private:
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static const int SIZE_DICT = 256;
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// Make sure the delimiter you choose is not among the charset of the encoding/decoding scheme.
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// Otherwise you'll have to use escaped charaters to avoid ambiguity.
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static const char CHAR_WORD_DEL = '\0';
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static const char CHAR_SEQ_DEL = '\1';
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string b64;
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vector<int> bi;
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string encodeBase64(string &s) {
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// Any implementation is OK, base64 is just one option.
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int ls = s.size();
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string t = "";
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int i;
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int idx;
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int val;
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int bc;
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val = 0;
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bc = 0;
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i = 0;
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do {
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val = (val << 8) + s[i++];
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bc += 8;
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while (bc >= 6) {
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idx = (val >> bc - 6);
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val &= (1 << bc - 6) - 1;
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t.push_back(b64[idx]);
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bc -= 6;
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}
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} while (i < ls);
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if (bc > 0) {
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val <<= (6 - bc);
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idx = val;
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t.push_back(b64[idx]);
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bc = 0;
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}
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// Padding with '=' is unnecessary if you got other delimiters in place.
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return t;
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}
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string decodeBase64(string &s) {
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// Any implementation is OK, base64 is just one option.
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int ls = s.size();
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string t = "";
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int i;
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int idx;
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int val;
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int bc;
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val = 0;
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bc = 0;
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i = 0;
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do {
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val = (val << 6) + bi[s[i++]];
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bc += 6;
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while (bc >= 8) {
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idx = (val >> (bc - 8));
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val &= (1 << (bc - 8)) - 1;
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t.push_back(idx);
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bc -= 8;
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}
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} while (i < ls);
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return t;
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}
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};
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// Your Codec object will be instantiated and called as such:
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// Codec codec;
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// codec.decode(codec.encode(strs));

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