path-sum-ii

题目：

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 andsum = 22,
5
/ \
4 8
/ / \
11 13 4
/ \ / \
7 2 5 1
return
[
[5,4,11,2],
[5,8,4,5]
]

程序：

class Solution {
public:
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        vector<vector<int>> res;
        if(root==NULL)
            return res;
        solve(res,root,sum);
        return res;
    }

    void solve(vector<vector<int>> &res,TreeNode *root,int sum)
    {
        if(root&&root->left==NULL&&root->right==NULL&&sum==root->val)
        {
            v.push_back(root->val);
            res.push_back(v);
            v.pop_back();
            return;
        }
        if(root==NULL)
            return;
        v.push_back(root->val);
        solve(res,root->left,sum-root->val);
        solve(res,root->right,sum-root->val);
        v.pop_back();
    }

    vector<int> v;
};