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 path 5->4->11->2 which sum is 22.
java代码：
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
private boolean stop = false;
public boolean hasPathSum(TreeNode root, int sum) {
calculate(root, 0, sum);
return stop;
}
private void calculate(TreeNode node, int cur, int sum) {
if (!stop && node != null) {
if (node.left == null && node.right == null && (node.val + cur == sum)) {
stop = true;
}
if (node.left != null) {
calculate(node.left, cur+node.val, sum);
}
if (node.right != null) {
calculate(node.right, cur+node.val, sum);
}
}
}
}
