leetcode--40. Combination Sum II

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

Each number in C may only be used once in the combination.

Note:

• All numbers (including target) will be positive integers.
• The solution set must not contain duplicate combinations.

For example, given candidate set [10, 1, 2, 7, 6, 1, 5] and target 8, 

A solution set is: 

[  [1, 7],  [1, 2, 5],  [2, 6],  [1, 1, 6]]

class Solution {public:    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {        //Don't disturbing the original array        vector<int> can(candidates.begin(), candidates.end());                //!!! Here needs to sort the array, because we need to jump the same elements        sort(can.begin(), can.end());                //Backtracing        vector<vector<int>> ret;        vector<int> tmp;        bt(can, tmp, target, 0, ret);        return ret;    }    private:    void bt(vector<int> &can, vector<int> &tmp, int target, int start, vector<vector<int>> &ret){        if(target < 0) return;        if(target == 0) ret.push_back(tmp);        for(int i = start; i<can.size(); i++){            if(i > start && can[i] == can[i-1]) continue; //To jump the same element            tmp.push_back(can[i]);            //Next tracing should input i+1, because reuse is illeagal            bt(can, tmp, target-can[i], i+1, ret);             tmp.pop_back();        }    }};