LeetCode OJ:Combination Sum

Combination Sum

 

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

• All numbers (including target) will be positive integers.
• Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
• The solution set must not contain duplicate combinations.

For example, given candidate set 2,3,6,7 and target 7, 
A solution set is: 
[7] 
[2, 2, 3] 

算法思想：暴搜

class Solution {    vector<vector<int> > result;     vector<int> res; public:    void dfs(vector<int>& candidates, int target, int start) {        if (target <= 0) {            if(target == 0){                result.push_back(res);            }            return;        }        for (int i = start; i < candidates.size(); i++) {            res.push_back(candidates[i]);             dfs(candidates, target - candidates[i], i);            res.pop_back();        }    }    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {        sort(candidates.begin(), candidates.end());        dfs(candidates, target, 0);        return result;    }};