【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=0)
    {
        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);
    }
};