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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 path 5->4->11->2 which sum is 22.

C++版

class Solution {public:    bool hasPathSum(TreeNode *root, int sum) {        if (root == NULL) return false;          if (root->left == NULL && root->right == NULL && sum - root->val == 0) return true;          return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);              }   };

Java版本:

/** * 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;          if (root.left == null && root.right == null && sum - root.val == 0) return true;          return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);              }  }  

  

Path Sum