[LeetCode] Path Sum II 深度搜索

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]
]

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　　　这题其实就是深度搜索，代码：

#include <vector>
#include <iostream>
using namespace std;
/**
 * 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> > ret;
    vector<int> nowPath;
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        ret.clear();
        nowPath.clear();
        if(root==NULL)  return ret;
        help_f(root,sum);
        return ret;
    }

    void help_f(TreeNode *root,int sum)
    {
        if(root==NULL)  return ;
        nowPath.push_back(root->val);
        help_f(root->left,sum - root->val);
        help_f(root->right,sum - root->val);
        if(root->left==NULL&&root->right==NULL&&sum==root->val)
            ret.push_back(nowPath);
        nowPath.pop_back();
    }
};

int main()
{
    return 0;
}