【leetcode】Path Sum II

Path Sum II

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,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

 

 

采用深度优先搜索即可

 

 /**
  * Definition for binary tree
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Solution {
 public:
     vector<vector<int> > pathSum(TreeNode *root, int sum) {
         vector<int> tmp;
         vector<vector<int> > result;
         if(root==NULL)
         {
             return result;
         }
         DFS(root,sum,tmp,result);
         return result;

     }

     void DFS(TreeNode *root,int &sum, vector<int> tmp,vector<vector<int> > &result,int cur=)
     {
         if(root==NULL)
         {
             return;
         }

         int val=root->val;
         tmp.push_back(val);

         if(root->left==NULL&&root->right==NULL)
         {
             if(cur+val==sum) result.push_back(tmp);
             return;
         }
         DFS(root->left,sum,tmp,result,cur+val);
         DFS(root->right,sum,tmp,result,cur+val);
     }
 };