[LeetCode]Path Sum II

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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]]

分析：典型DFS。

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {private:     vector<vector<int>> ret;public:    vector<vector<int>> pathSum(TreeNode* root, int sum) {        if(root==NULL)            return ret;        vector<int> temp;        dfs(root,sum,temp);        return ret;    }    void dfs(TreeNode* root,int sum,vector<int> temp){        temp.push_back(root->val);        if(root->val==sum&&root->right==NULL&&root->left==NULL)            ret.push_back(temp);        if(root->left)            dfs(root->left,sum-(root->val),temp);        if(root->right)            dfs(root->right,sum-(root->val),temp);    }};

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