没有懂的leetcode

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.
• 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 10,1,2,7,6,1,5 and target 8, 
A solution set is: 
[1, 7] 
[1, 2, 5] 
[2, 6] 
[1, 1, 6]

public class Solution {
    public IList<IList<int>> CombinationSum2(int[] candidates, int target) {
        List<IList<int>> result = new List<IList<int>>();
        List<int> res=new List<int>();
        Array.Sort(candidates);
        calulate(candidates,,target,res,result);
        return result;
    }

    void calulate(int[] candidates, int cur,int target,List<int> res,List<IList<int>> result)
    {
        )
        {
            result.Add(new List<int>(res));
            return;
        }
        )
        {
            return;
        }

        for(int i=cur;i<candidates.Length;i++)
        {
           ])
              continue;
           res.Insert(res.Count,candidates[i]);
           calulate(candidates,i+,target-candidates[i],res,result);
           res.RemoveAt(res.Count-);
        }
    }
}

1 这个算法可以非常高效的计算出结果。

2 这个算法是在方法中调用方法本身。