LeetCode 113 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.

Note: A leaf is a node with no children.

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]
]


c++

class Solution {

public:
    vector<vector<int> > result;
    
    vector<vector<int> > pathSum(TreeNode* root, int sum) {
        
        if(root==NULL) return result;
        vector<int> a;
        dfs(root,sum,a);
        return result;
        
    }
    
    void dfs(TreeNode* root,int sum,vector<int>a)
    {
        a.push_back(root->val);
        if(root->left==NULL&&root->right==NULL)
        {
            if(sum==root->val)
                result.push_back(a);
        }
        if(root->left!=NULL)
            dfs(root->left,sum-root->val,a);
        if(root->right!=NULL)
            dfs(root->right,sum-root->val,a);
    }
};