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anishLearnsToCodeanishLearnsToCode
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solves #547: Number of Provinces in java
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‎README.md

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| 538 | [Convert BST to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree) | [![Java](assets/java.png)](src/ConvertBSTToGreaterTree.java) [![Python](assets/python.png)](python/convert_bst_to_greater_tree.py) | |
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| 541 | [Reverse String II](https://leetcode.com/problems/reverse-string-ii) | [![Java](assets/java.png)](src/ReverseStringII.java) [![Python](assets/python.png)](python/reverse_string_ii.py) | |
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| 543 | [Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree) | [![Java](assets/java.png)](src/DiameterOfBinaryTree.java) [![Python](assets/python.png)](python/diameter_of_binary_tree.py) | |
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| 547 | [Number of Provinces](https://leetcode.com/problems/number-of-provinces) | [![Java](assets/java.png)](src/NumberOfProvinces.java) | |
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| 551 | [Student Attendance Record I](https://leetcode.com/problems/student-attendance-record-i) | [![Java](assets/java.png)](src/StudentAttendanceRecordI.java) [![Python](assets/python.png)](python/student_attendance_record_I.py) | |
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| 557 | [Reverse Words in a String III](https://leetcode.com/problems/reverse-words-in-a-string-iii) | [![Java](assets/java.png)](src/ReverseWordsInStringIII.java) [![Python](assets/python.png)](python/reverse_words_in_string_iii.py) | |
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| 559 | [Maximum Depth of N-Ary Tree](https://leetcode.com/problems/maximum-depth-of-n-ary-tree) | [![Java](assets/java.png)](src/MaximumDepthOfNAryTree.java) [![Python](assets/python.png)](python/maximum_depth_of_n_ary_tree.py) | |

‎src/HelloWorld.java

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import java.util.*;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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import java.util.Queue;
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import java.util.Set;
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/*
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kahns algorithm
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t: O(V + E)
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S: O(E)
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*/
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public class HelloWorld {
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public static class Node {
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public int val;
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public List<Node> neighbors;
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public Node() {
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val = 0;
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neighbors = new ArrayList<>();
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private static class QuickUnionFind {
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private final int[] array;
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public QuickUnionFind(int size) {
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array = new int[size];
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for (int i = 0 ; i < array.length ; i++) {
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array[i] = i;
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}
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}
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public Node(int _val) {
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val = _val;
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neighbors = new ArrayList<>();
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public void union(int x, int y) {
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final int rootX = find(x), rootY = find(y);
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if (rootY == rootX) {
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return;
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}
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for (int i = 0 ; i < array.length ; i++) {
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if (array[i] == rootY) {
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array[i] = rootX;
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}
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}
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}
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public Node(int _val, ArrayList<Node> _neighbors) {
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val = _val;
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neighbors = _neighbors;
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public int find(int num) {
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return array[num];
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}
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@Override
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public String toString() {
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return "Node{" +
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"val=" + val +
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'}';
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public boolean areConnected(int x, int y) {
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return find(x) == find(y);
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}
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}
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public static Node cloneGraph(Node root) {
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final Queue<Node> queue = new LinkedList<>();
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final Map<Node, Node> oldToNew = new HashMap<>();
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final Set<Node> processed = new HashSet<>();
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queue.add(root);
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private static final class QuickUnionDisjointSet {
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private final int[] array;
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while (!queue.isEmpty()) {
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final Node node = queue.poll();
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if (processed.contains(node)) {
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continue;
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public QuickUnionDisjointSet(int size) {
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array = new int[size];
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for (int i = 0 ; i < array.length ; i++) {
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array[i] = i;
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}
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processed.add(node);
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final Node newNode = oldToNew.getOrDefault(node, new Node(node.val));
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oldToNew.putIfAbsent(node, newNode);
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}
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for (Node edge : node.neighbors) {
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final Node newEdge = oldToNew.getOrDefault(edge, new Node(edge.val));
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oldToNew.putIfAbsent(edge, newEdge);
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newNode.neighbors.add(newEdge);
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queue.add(edge);
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public int find(int num) {
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while (array[num] != num) {
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num = array[num];
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}
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return num;
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}
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return oldToNew.get(root);
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}
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public boolean areConnected(int x, int y) {
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return find(x) == find(y);
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}
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public static void main(String[] args) {
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final Node node1 = new Node(1);
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final Node node2 = new Node(2);
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final Node node3 = new Node(3);
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final Node node4 = new Node(4);
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public void union(int x, int y) {
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final int rootX = find(x), rootY = find(y);
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if (rootX == rootY) {
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return;
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}
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array[rootY] = rootX;
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}
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}
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node1.neighbors.add(node2);
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node1.neighbors.add(node4);
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private static final class DisjointSetRank {
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private final int[] array;
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private final int[] rank;
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node2.neighbors.add(node1);
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node2.neighbors.add(node3);
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public DisjointSetRank(int size) {
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array = new int[size];
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rank = new int[size];
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for (int i = 0 ; i < array.length ; i++) {
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rank[i] = 1;
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array[i] = i;
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}
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}
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node3.neighbors.add(node2);
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node3.neighbors.add(node4);
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// T: O(logN)
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// S: O(1)
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public int find(int num) {
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if (num == array[num]) {
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return num;
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}
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final int root = find(array[num]);
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array[num] = root;
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return root;
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}
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node4.neighbors.add(node1);
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node4.neighbors.add(node3);
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// T: O(logN)
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// S: O(1)
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public void union(int x, int y) {
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final int rootX = find(x), rootY = find(y);
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if (rootX == rootY) {
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return;
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}
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if (rank[rootX] > rank[rootY]) {
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array[rootY] = rootX;
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} else if (rank[rootX] < rank[rootY]) {
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array[rootX] = rootY;
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} else {
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array[rootY] = rootX;
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rank[rootX]++;
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}
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}
72120

73-
final Node clone = cloneGraph(node1);
74-
System.out.println(clone);
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// T: O(logN)
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// S: O(1)
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public boolean areConnected(int x, int y) {
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return find(x) == find(y);
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}
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}
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}
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}

‎src/NumberOfProvinces.java

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// https://leetcode.com/problems/number-of-provinces
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// T: O(N^2)
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// S: O(N)
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public class NumberOfProvinces {
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private static final class DisjointSet {
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private final int[] array, rank;
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public DisjointSet(int size) {
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this.array = new int[size];
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this.rank = new int[size];
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for (int i = 0 ; i < size ; i++) {
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array[i] = i;
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rank[i] = 1;
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}
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}
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// T: O(1)
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public int find(int x) {
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if (x == array[x]) {
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return x;
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}
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final int rank = find(array[x]);
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array[x] = rank;
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return rank;
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}
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// T: O(1)
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public boolean areConnected(int x, int y) {
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return find(x) == find(y);
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}
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// T: O(1)
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public void union(int x, int y) {
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final int rootX = find(x), rootY = find(y);
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if (rootX == rootY) {
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return;
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}
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if (array[rootX] > array[rootY]) {
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array[rootY] = rootX;
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} else if (array[rootX] < array[rootY]) {
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array[rootX] = rootY;
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} else {
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array[rootY] = rootX;
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rank[rootX]++;
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}
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}
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private int size() {
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return array.length;
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}
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}
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// T: O(n^2)
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public int findCircleNum(int[][] isConnected) {
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final int cities = isConnected.length;
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final DisjointSet disjointSet = new DisjointSet(cities);
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int provinces = cities;
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for (int i = 0 ; i < cities ; i++) {
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for (int j = i + 1 ; j < cities ; j++) {
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if (isConnected[i][j] == 1 && disjointSet.find(i) != disjointSet.find(j)) {
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disjointSet.union(i, j);
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provinces--;
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}
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}
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}
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return provinces;
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}
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}

‎src/SnakesAndLadders.java

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// https://leetcode.com/problems/snakes-and-ladders
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// T: O()
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// S: O()
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public class SnakesAndLadders {
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}

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