LeetCode之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.

              5
             /             4   8
           /   /           11  13  4
         /  \    /         7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

回溯法的思想。

/**
 * 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> > pathSum(TreeNode *root, int sum) {
        vector<vector<int>> rstv;
        vector<int> tmpv;
        findSub(root,sum,rstv,tmpv);
        return rstv;
    }
    
    void findSub(TreeNode*root,int sum,vector<vector<int>> &rstv,vector<int> &tmpv){
         if (!root) return;
		 tmpv.push_back(root->val);
		 if (!root->left && !root->right && root->val == sum){
			 rstv.push_back(tmpv);
			 tmpv.pop_back();
			 return;
		 }
		 if (root->left)   findSub(root->left, sum-root->val, rstv, tmpv);
		 if (root->right)   findSub(root->right, sum - root->val, rstv, tmpv);
		 tmpv.pop_back();
    }
};