LeetCode-112-Path Sum(路径和)

Q:

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.

Analysis:

题目要求给出路径和，判断二叉树根到叶子结点是否有累加和等于路径和的分支。

采用递归方法，依次递归每个分支，直到有相等的分值为止。

Code:

/**
* Definition for a binary tree node.
* 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;
} else if (root.left == null && root.right == null && root.val == sum) {// 递归结束条件
return true;
} else {
return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
}
}
}