Given a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum.
For example:
Given the below binary tree and sum = 22,

return

这个题目适合用递归来解，我的C++代码实现如下：

class Solution {
public:
    vector
   
     > pathSum(TreeNode *root, int sum) { vector
    
      > paths; vector
     
       curr_path; if (!root) return paths; find(root, sum, paths, curr_path); return paths; } private: void find(TreeNode *root, int sum, vector
      
        > &paths, vector
       
         &curr_path) { curr_path.push_back(root->val); if (root->left == nullptr && root->right == nullptr) if (root->val == sum) paths.push_back(curr_path); if (root->left) { find(root->left, sum - root->val, paths, curr_path); curr_path.pop_back(); } if (root->right) { find(root->right, sum - root->val, paths, curr_path); curr_path.pop_back(); } } };
       
      
     
    
   

时间性能如下图所示：