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by Sumit Chourasia | Oct 25, 2020 | Category :coding | Tags : algorithm array data-structure leetcode medium

Combination Sum II - Array - Medium - LeetCode

Combination Sum II - Array - Medium - LeetCode

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

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

Note: The solution set must not contain duplicate combinations.

 

Example 1:

Input: candidates = [10,1,2,7,6,1,5], target = 8
Output: 
[
[1,1,6],
[1,2,5],
[1,7],
[2,6]
]
Example 2:

Input: candidates = [2,5,2,1,2], target = 5
Output: 
[
[1,2,2],
[5]
]
 

Constraints:

1 <= candidates.length <= 100
1 <= candidates[i] <= 50
1 <= target <= 30

public class Solution {
    IList<IList<int>> ans = new List<IList<int>>();    
    HashSet<string> set = new HashSet<string>();
    public IList<IList<int>> CombinationSum2(int[] candidates, int target) {
        var res = new List<int>();        
        Array.Sort(candidates);
              
        Helper(candidates, target, res, 0);
        return ans;
    }
    
    private void Helper(int[] candidates, int target, List<int> res, int start){
        if(target == 0){           
            var temp = new List<int>();
            foreach(var item in res){
                temp.Add(item);
            }
            ans.Add(temp);            
            return;
        }
        
        if(target < 0)
        {
            return;
        }
        
        for(int i=start;i<candidates.Length;i++){ 
            if(i>start && candidates[i]==candidates[i-1]){
                continue;
            }            
            res.Add(candidates[i]);            
            Helper(candidates, target-candidates[i], res, i+1);
            res.RemoveAt(res.Count()-1);          
        }
    }
    
}

Time Complexity: O(2^n)

Space Complexity: O(1)