【LeetCode】C# 39、Combination Sum

Given a set of candidate numbers (C) (without duplicates) 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.
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]
]

给定数组和目标值，数组中的个别值拼凑求和，把所有符合条件的组合返回。

思路：DP

public class Solution {    public List<List<int>> CombinationSum(int[] candidates, int target) {        Array.Sort(candidates);        List<List<int>> result = new List<List<int>>();        getResult(result, new List<int>(), candidates, target, 0);        return result;    }    private void getResult(List<List<int>> result, List<int> cur, int[] candidates, int target, int start){        if(target > 0){            for(int i = start; i < candidates.Length && target >= candidates[i]; i++){                cur.Add(candidates[i]);                getResult(result, cur, candidates, target - candidates[i], i);                cur.RemoveAt(cur.Count() - 1);            }        }        else if(target == 0 ){            result.Add(new List<int>(cur));        }    }}

思路2：动态规划。
参考自
http://www.cnblogs.com/etcow/archive/2012/07/03/2575443.html

public static List<List<int>> CominationSum(int[] candidates, int target)        {            Dictionary<int, List<List<int>>> map = new Dictionary<int, List<List<int>>>();            //Array.Sort(candidates);            for (int cur_sum = 1; cur_sum <= target; cur_sum++)            {                for (int cand_index = 0; cand_index < candidates.Length; cand_index++)                {                    if (cur_sum < candidates[cand_index])                        continue;                    if (cur_sum == candidates[cand_index])                    {                        List<int> templist = new List<int> { candidates[cand_index] };                        if (map.ContainsKey(cur_sum))                            map[cur_sum].Add(templist);                        else                        {                            List<List<int>> templistlist = new List<List<int>>();                            templistlist.Add(templist);                            map.Add(cur_sum, templistlist);                        }                        continue;                    }                    int pre_cur_sum = cur_sum - candidates[cand_index];                    if (!map.ContainsKey(pre_cur_sum))                        continue;                    else                    {                        int pre_cur_sum_size = map[pre_cur_sum].Count;                        for (int i = 0; i < pre_cur_sum_size; i++)                        {                            if (map[pre_cur_sum][i][map[pre_cur_sum][i].Count - 1] <= candidates[cand_index])                            {                                List<int> templist = new List<int>(map[pre_cur_sum][i]);                                templist.Add(candidates[cand_index]);                                if (map.ContainsKey(cur_sum))                                    map[cur_sum].Add(templist);                                else                                {                                    List<List<int>> templistlist = new List<List<int>>();                                    templistlist.Add(templist);                                    map.Add(cur_sum, templistlist);                                }                            }                        }                    }                }            }            return map[target];        }

这两个思路C#解都能在VS跑出来，但LeetCode都没AC，因为LeetCode不接受返回格式为List<List<int>>只能为IList<IList<int>>，我不知道怎么初始化，烦请知道怎么解决的朋友赐教。