[leetcode]113. Path Sum II

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题目链接：https://leetcode.com/problems/path-sum-ii/#/description

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]
]

class Solution{
public:
    vector<vector<int>> pathSum(TreeNode* root,int sum)
    {
        vector<vector<int>> res;
        vector<int> tmp;
        dfs(res,tmp,root,sum);
        return res;
    }
    void dfs(vector<vector<int>>& res,vector<int> tmp,TreeNode* root,int sum)
    {
        if(root==NULL)
            return;
        tmp.push_back(root->val);
        sum-=root->val;
        if(sum==0 && root->left==NULL && root->right==NULL)
        {
            res.push_back(tmp);
            return;
        }
        if (root->left)
            dfs(res,tmp,root->left,sum);
        if(root->right)
            dfs(res,tmp,root->right,sum);
        tmp.pop_back();
    }
};

class Solution{
public:
    vector<vector<int>> pathSum(TreeNode* root,int sum)
    {
        vector<vector<int>> res;
        vector<int> tmp;
        dp(res,tmp,root,sum);
        return res;
    }

    void dp(vector<vector<int>>& res,vector<int> tmp,TreeNode*root,int sum)
    {
        if(!root)
            return;
        tmp.push_back(root->val);
        if(!root->left && !root->right)
        {
            if(accumulate(tmp.begin(),tmp.end(),0)==sum)
                res.push_back(tmp);
            return;
        }
        dp(res,tmp,root->left,sum);
        dp(res,tmp,root->right,sum);
    }
};