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
class Solution { public: bool hasPathSum(TreeNode *root, int sum) { if(root == NULL) { return false; } if(root->left == NULL && root->right == NULL) //判断叶节点 { if(root->val == sum) return true; return false; } if ( hasPathSum(root->left, sum - root->val) // 递归 || hasPathSum(root->right, sum - root->val) ) return true; return false; } };
原文：http://www.cnblogs.com/diegodu/p/4413931.html