40. Combination Sum II

Problem Statement

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

Intuition

Approach:

Do unique values, can make use of set, but gives TLE

So,
We Pick element at one index, only once
Like, 

1 1 2 3 
If at once we pick 1, we dont pick it again until next iteration

Links

https://leetcode.com/problems/combination-sum-ii/description/

Video Links

https://www.youtube.com/watch?v=G1fRTGRxXU8&t=1244s&ab_channel=takeUforward

Approach 1:

C++

class Solution {
public:
    vector<vector<int>> ans;
    void find_comb(vector<int>& cand, int target, int index, vector<int> &temp){
        if(target == 0){
            ans.push_back(temp);
            return ;
        }

        for(int i=index; i<cand.size(); i++){
            if(i > index and cand[i-1] == cand[i])
                continue; 

            if(cand[i] > target)    break;

            temp.push_back(cand[i]);
            find_comb(cand, target-cand[i], i+1, temp);
            temp.pop_back();
        }
    }

    vector<vector<int>> combinationSum2(vector<int>& cand, int target) {
        vector<int> temp;
        sort(cand.begin(), cand.end());
        find_comb(cand, target, 0, temp);

        return ans;
    }
};

Approach 2:

C++

Approach 3:

C++

Approach 4:

C++