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solves #399: Evaluate Division in java
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‎README.md

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| 387 | [First Unique Character in String](https://leetcode.com/problems/first-unique-character-in-a-string) | [![Java](assets/java.png)](src/FirstUniqueCharacter.java) [![Python](assets/python.png)](python/first_unique_character_in_string.py) | |
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| 389 | [Find the Difference](https://leetcode.com/problems/find-the-difference) | [![Java](assets/java.png)](src/FindTheDifference.java) [![Python](assets/python.png)](python/find_the_difference.py) | |
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| 392 | [Is Subsequence](https://leetcode.com/problems/is-subsequence) | [![Java](assets/java.png)](src/IsSubsequence.java) [![Python](assets/python.png)](python/is_subsequence.py) | |
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| 399 | [Evaluate Division](https://leetcode.com/problems/evaluate-division) | [![Java](assets/java.png)](src/EvaluateDivision.java) | |
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| 401 | [Binary Watch](https://leetcode.com/problems/binary-watch) | [![Java](assets/java.png)](src/BinaryWatch.java) [![Python](assets/python.png)](python/binary_watch.py) | |
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| 404 | [Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves) | [![Java](assets/java.png)](src/SumOfLeftLeaves.java) [![Python](assets/python.png)](python/sum_of_left_leaves.py) | |
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| 405 | [Convert a Number to Hexadecimal](https://leetcode.com/problems/convert-a-number-to-hexadecimal) | [![Java](assets/java.png)](src/ConvertNumberToHexadecimal.java) [![Python](assets/python.png)](python/convert_a_number_to_hexadecimal.py) | |

‎src/EvaluateDivision.java

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// https://leetcode.com/problems/evaluate-division
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// N = |equations|, M = |queries|
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// T: O(N + M*N) = O(MN)
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// S: O(N + M)
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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public class EvaluateDivision {
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public static double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
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final Map<String, Map<String, Double>> graph = createGraph(equations, values);
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return computeQueries(graph, queries);
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}
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private static Map<String, Map<String, Double>> createGraph(List<List<String>> equations, double[] values) {
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final Map<String, Map<String, Double>> result = new HashMap<>();
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for (int i = 0 ; i < equations.size() ; i++) {
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final List<String> equation = equations.get(i);
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final String dividend = equation.get(0), divisor = equation.get(1);
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result.putIfAbsent(dividend, new HashMap<>());
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result.putIfAbsent(divisor, new HashMap<>());
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result.get(dividend).put(divisor, values[i]);
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result.get(divisor).put(dividend, 1 / values[i]);
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}
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return result;
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}
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private static double[] computeQueries(Map<String, Map<String, Double>> graph, List<List<String>> queries) {
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final double[] result = new double[queries.size()];
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for (int i = 0 ; i < queries.size() ; i++) {
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final List<String> query = queries.get(i);
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final String dividend = query.get(0), divisor = query.get(1);
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if (!graph.containsKey(dividend) || !graph.containsKey(divisor)) {
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result[i] = -1;
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} else if (dividend.equals(divisor)) {
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result[i] = 1;
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} else {
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result[i] = computeDfs(graph, dividend, divisor);
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}
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}
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return result;
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}
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private static double computeDfs(Map<String, Map<String, Double>> graph, String dividend, String divisor) {
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return dfs(graph, dividend, divisor, 1, new HashSet<>());
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}
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private static double dfs(Map<String, Map<String, Double>> graph, String current, String target, double product, Set<String> visited) {
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if (current.equals(target)) {
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return product;
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}
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if (visited.contains(current)) {
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return -1;
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}
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visited.add(current);
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for (Map.Entry<String, Double> edges : graph.get(current).entrySet()) {
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final double result = dfs(graph, edges.getKey(), target, product * edges.getValue(), visited);
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if (result != -1) {
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return result;
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}
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}
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return -1;
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}
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}

‎src/HelloWorld.java

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import java.util.*;
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public class HelloWorld {
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public int countNodes(TreeNode root) {
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if (root == null) {
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return 0;
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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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}
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final int depth = depthTree(root) - 1;
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if (depth == 0) {
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return 1;
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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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}
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int left = 0, right = (int) Math.pow(2, depth) - 1, middle;
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while (left <= right) {
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middle = left + (right - left) / 2;
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if (exists(root, depth, middle)) left = middle + 1;
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else right = middle - 1;
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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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}
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return (int) Math.pow(2, depth) - 1 + left;
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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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}
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}
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private static boolean exists(TreeNode root, int depth, int index) {
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TreeNode current = root;
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int value = -1;
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for (int i = 0 ; i < depth ; i++) {
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final int middle = (int) Math.pow(2, depth - 1 - i);
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if (index > value + middle) {
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current = current.right;
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value += middle;
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} else {
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current = current.left;
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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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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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}
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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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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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}
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}
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return current != null;
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return oldToNew.get(root);
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}
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private static int depthTree(TreeNode root) {
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if (root == null) {
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return 0;
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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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node1.neighbors.add(node2);
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node1.neighbors.add(node4);
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node2.neighbors.add(node1);
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node2.neighbors.add(node3);
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node3.neighbors.add(node2);
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node3.neighbors.add(node4);
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node4.neighbors.add(node1);
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node4.neighbors.add(node3);
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return 1 + Math.max(depthTree(root.left), depthTree(root.right));
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final Node clone = cloneGraph(node1);
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System.out.println(clone);
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}
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}
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}

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