LeetCode 112 Path Sum

Source: Internet
Author: User

LeetCode 112 Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,
              5             / \            4   8           /   / \          11  13  4         /  \      \        7    2      1

Return true, as there exist a root-to-leaf path5->4->11->2Which sum is 22.

Idea: use sequential traversal, but I changed the node value when I pressed the stack.

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {public boolean hasPathSum(TreeNode root, int sum) {    if(root == null ) return false;Stack
   s = new Stack
   ();s.push(root);while (!s.isEmpty()) {TreeNode temp = s.peek();s.pop();if (temp.right != null) {temp.right.val += temp.val;s.push(temp.right);}if (temp.left != null) {temp.left.val += temp.val;s.push(temp.left);}if (temp.left == null && temp.right == null && temp.val == sum)return true;}return false;}}

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