leetcode解题: Combination Sum II (40)

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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]
]

解法1：

这题和Combination Sum的唯一区别是每一个数字只能使用一次，那么每一次挑选的时候无论是否有解都往前进一格就可以了。
C++

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class Solution {
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
    vector<vector<int>> res;
    vector<int> current;
    sort(candidates.begin(),candidates.end());
    backTracking(candidates.begin(),current,res,candidates,target);
    return res;
}
void backTracking(vector<int>::iterator n, vector<int>& current,vector<vector<int>>& res, const vector<int>& candidates, int target){
    if(!target) res.push_back(current);
    else if(target>0){
        for(;n!=candidates.end()&&*n<=target;++n){
            current.push_back(*n);
            backTracking(n+1,current,res,candidates,target-*n);
            current.pop_back();
            while(n+1!=candidates.end()&&*(n+1)==*n) ++n;
        }
    }
}
};

Java

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