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->2
Which 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;}}