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  • paginated_contents/algorithms/4th_thousand
  • src/main/java/com/fishercoder/solutions/fourththousand

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‎paginated_contents/algorithms/4th_thousand/README.md

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| # | Title | Solutions | Video | Difficulty | Tag
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|------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------|------------|----------------------------------------------------------------------
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| 3249 | [Count the Number of Good Nodes](https://leetcode.com/problems/count-the-number-of-good-nodes/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3249.java) | | Medium |
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| 3248 | [Snake in Matrix](https://leetcode.com/problems/snake-in-matrix/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3248.java) | | Easy |
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| 3243 | [Shortest Distance After Road Addition Queries I](https://leetcode.com/problems/shortest-distance-after-road-addition-queries-i/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3243.java) | | Medium |
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| 3242 | [Design Neighbor Sum Service](https://leetcode.com/problems/design-neighbor-sum-service/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3242.java) | | Easy |

‎src/main/java/com/fishercoder/solutions/fourththousand/_3249.java

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package com.fishercoder.solutions.fourththousand;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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public class _3249 {
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public static class Solution1 {
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/**
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* My completely original solution during the contest.
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*/
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class TreeNode {
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int val;
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List<TreeNode> children;
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int totalChildrenCount;
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public TreeNode(int val) {
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this.val = val;
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this.children = new ArrayList<>();
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this.totalChildrenCount = 1;//count itself as its own child
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}
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}
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int goodNodes = 0;
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public int countGoodNodes(int[][] edges) {
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if (edges == null || edges.length == 0 || edges[0].length == 0) {
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return 0;
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}
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TreeNode root = buildTree(edges);
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postOrder(root);
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dfs(root);
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return goodNodes;
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}
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private void dfs(TreeNode root) {
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if (root == null || root.children.isEmpty()) {
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return;
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}
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int size = root.children.get(0).totalChildrenCount;
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if (size == 0) {
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return;
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}
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boolean possiblyGoodNode = true;
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for (TreeNode child : root.children) {
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if (child.totalChildrenCount != size) {
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possiblyGoodNode = false;
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break;
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}
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}
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if (possiblyGoodNode) {
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goodNodes++;
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}
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for (TreeNode child : root.children) {
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dfs(child);
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}
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}
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private int postOrder(TreeNode root) {
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if (root == null) {
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return 0;
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}
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if (root.children.isEmpty()) {
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goodNodes++;
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return 1;
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}
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int totalChildrenCount = 1;
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for (TreeNode child : root.children) {
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int count = postOrder(child);
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totalChildrenCount += count;
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}
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root.totalChildrenCount = totalChildrenCount;
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return totalChildrenCount;
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}
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private TreeNode buildTree(int[][] edges) {
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Map<Integer, TreeNode> map = new HashMap<>();
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for (int i = 0; i < edges.length; i++) {
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if (edges[i][0] == 0 || edges[i][1] == 0) {
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if (edges[i][0] == 0) {
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TreeNode parent = map.getOrDefault(edges[i][0], new TreeNode(edges[i][0]));
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TreeNode child = map.getOrDefault(edges[i][1], new TreeNode(edges[i][1]));
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parent.children.add(child);
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map.put(edges[i][0], parent);
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map.put(edges[i][1], child);
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} else {
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TreeNode parent = map.getOrDefault(edges[i][1], new TreeNode(edges[i][1]));
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TreeNode child = map.getOrDefault(edges[i][0], new TreeNode(edges[i][0]));
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parent.children.add(child);
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map.put(edges[i][1], parent);
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map.put(edges[i][0], child);
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}
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} else {
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if (map.containsKey(edges[i][0])) {
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TreeNode parent = map.get(edges[i][0]);
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TreeNode child = map.getOrDefault(edges[i][1], new TreeNode(edges[i][1]));
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parent.children.add(child);
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map.put(edges[i][0], parent);
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map.put(edges[i][1], child);
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} else if (map.containsKey(edges[i][1])) {
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TreeNode parent = map.get(edges[i][1]);
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TreeNode child = map.getOrDefault(edges[i][0], new TreeNode(edges[i][0]));
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parent.children.add(child);
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map.put(edges[i][1], parent);
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map.put(edges[i][0], child);
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}
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}
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}
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return map.get(0);
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}
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}
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}

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