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.
/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: bool hasPathSum(TreeNode *root, int sum) { bool flag = false; level(root,0,sum,flag); return flag; } void level(TreeNode *node, int tmpsum, int sum, bool& flag) { if(flag) return; if(node == NULL) return; int newsum = tmpsum + node->val; if(newsum == sum && node->left == NULL && node->right == NULL){ flag = true; return; } else{ level(node->left, newsum, sum, flag); level(node->right, newsum, sum, flag); } } };
原文：http://www.cnblogs.com/code-swan/p/4141165.html