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: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.
Tree Depth-first Search
/** * 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) { if(root==NULL) //路不通 return false; if(sum-root->val==0 && root->left==NULL && root->right==NULL) //结束条件 return true; if(hasPathSum(root->left,sum-root->val)) return true; else return hasPathSum(root->right,sum-root->val); } };
原文：http://www.cnblogs.com/li303491/p/4108973.html