回溯Leetcode 40 Combination Sum II

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Leetcode 40

Combination Sum II

• Problem Description：
  经典回溯问题：给出一个集合，选取集合中的元素相加使得和等于给定的target值，返回所有满足情况的组合（对于同个元素最多可重复使用1次）
  具体的题目信息：
  https://leetcode.com/problems/combination-sum-ii/description/
• Example:
  
• Solution:

class Solution {
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        vector<int> t;
        vector<vector<int>> res;
        if (candidates.size() == 0) return res;
        sort(candidates.begin(), candidates.end());
        vector<int> p;
        combination(p, candidates, res, target, 0);
        return res;
    }
    void combination(vector<int>& p, vector<int>& candidates, vector<vector<int>>& res, int target, int i) {
        if (target<0) {
            return;
        } else if (target==0) {
            res.push_back(p);
            return;
        } else {
            for (int j = i; j < candidates.size(); j++) {
                if (j > i && candidates[j] == candidates[j-1]) continue;
                p.push_back(candidates[j]);
                combination(p, candidates, res, target-candidates[j], j+1);
                p.erase(p.begin()+p.size()-1);
            }
        }
    }
};