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anishLearnsToCodeanishLearnsToCode
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solves #129 in java
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‎README.md‎

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# LeetCode Algorithms
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![problems-solved](https://img.shields.io/badge/Problems%20Solved-490/2081-1f425f.svg)
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![problems-solved-java](https://img.shields.io/badge/Java-490/2081-1abc9c.svg)
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![problems-solved](https://img.shields.io/badge/Problems%20Solved-509/2081-1f425f.svg)
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![problems-solved-java](https://img.shields.io/badge/Java-509/2081-1abc9c.svg)
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![problems-solved-python](https://img.shields.io/badge/Python-185/2081-1abc9c.svg)
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[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](CONTRIBUTING.md)
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[![cp](https://img.shields.io/badge/also%20see-Competitve%20Programming-1f72ff.svg)](https://github.com/anishLearnsToCode/competitive-programming)
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| 122 | [Best Time to Buy and Sell Stocks II](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii) | [![Java](assets/java.png)](src/BestTimeToBuyAndSellStockII.java) [![Python](assets/python.png)](python/best_time_to_buy_and_sell_stock_ii.py) | |
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| 125 | [Valid Palindrome](https://leetcode.com/problems/valid-palindrome) | [![Java](assets/java.png)](src/ValidPalindrome.java) [![Python](assets/python.png)](python/valid_palindrome.py) | |
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| 128 | [Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence) | [![Java](assets/java.png)](src/LongestConsecutiveSequence.java) | |
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| 129 | [Sum Root to Leaf Numbers](https://leetcode.com/problems/sum-root-to-leaf-numbers) | | |
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| 129 | [Sum Root to Leaf Numbers](https://leetcode.com/problems/sum-root-to-leaf-numbers) | [![Java](assets/java.png)](src/SumRootToLeafNumbers.java) | |
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| 130 | [Surrounded Regions](https://leetcode.com/problems/surrounded-regions) | | |
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| 131 | [Palindrome Partitioning](https://leetcode.com/problems/palindrome-partitioning) | | |
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| 133 | [Clone Graph](https://leetcode.com/problems/clone-graph) | | |

‎src/LongestConsecutiveSequence.java‎

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// T: O(n)
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// S: O(n)
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.Map;
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import java.util.Set;
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public class LongestConsecutiveSequence {
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private static class Node {
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Node next;
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Node previous;
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}
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public int longestConsecutive(int[] nums) {
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final Map<Integer, Node> nodes = createDisjointSets(nums);
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return longestConsecutiveSequenceLength(nodes);
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}
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private Map<Integer, Node> createDisjointSets(int[] array) {
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final Map<Integer, Node> result = new HashMap<>();
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for (int element : array) {
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if (result.containsKey(element)) continue;
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Node current = new Node();
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if (result.containsKey(element - 1)) {
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Node left = result.get(element - 1);
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left.next = current;
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current.previous = left;
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}
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if (result.containsKey(element + 1)) {
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Node right = result.get(element + 1);
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current.next = right;
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right.previous = current;
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}
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result.put(element, current);
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}
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return result;
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}
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private int longestConsecutiveSequenceLength(Map<Integer, Node> nodes) {
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final Set<Node> processedNodes = new HashSet<>();
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final Set<Integer> numbers = setFrom(nums);
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int maxLength = 0;
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for (Node node : nodes.values()) {
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int length = getLength(node, processedNodes);
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maxLength = Math.max(maxLength, length);
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for (int number : numbers) {
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if (!numbers.contains(number - 1)) {
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int length = 1;
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for (int i = number + 1 ; numbers.contains(i) ; i++) {
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length++;
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}
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maxLength = Math.max(maxLength, length);
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}
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}
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return maxLength;
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}
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private int getLength(Node node, Set<Node> processedNodes) {
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if (node == null) return 0;
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if (processedNodes.contains(node)) return 0;
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processedNodes.add(node);
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return 1 + getLength(node.previous, processedNodes) + getLength(node.next, processedNodes);
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private Set<Integer> setFrom(int[] array) {
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final Set<Integer> set = new HashSet<>();
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for (int element : array) {
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set.add(element);
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}
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return set;
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}
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}

‎src/SumRootToLeafNumbers.java‎

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// https://leetcode.com/problems/sum-root-to-leaf-numbers
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// T: O(n)
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// S: O(log(n))
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public class SumRootToLeafNumbers {
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public int sumNumbers(TreeNode root) {
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return sumNumbers(root, 0);
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}
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private int sumNumbers(TreeNode root, int currentSum) {
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if (root == null) return 0;
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if (isLeafNode(root)) return 10 * currentSum + root.val;
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return sumNumbers(root.left, 10 * currentSum + root.val)
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+ sumNumbers(root.right, 10 * currentSum + root.val);
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}
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private boolean isLeafNode(TreeNode root) {
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return root.left == null && root.right == null;
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}
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}

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