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Combination Sum II

Tags : array, backtracking, leetcode, cpp, medium

Problem Statement - link #

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.

Examples #

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 #

Solutions #

class Solution {
public:
    vector<vector<int>> res;
    vector<int> sub;
    void bc(vector<int>& c, int t, int i){
        if(t == 0) {
            res.push_back(sub);
            return;
        }
        for(int j=i; j<c.size(); j++){
            if(j>i and c[j]==c[j-1]) continue;
            if(t-c[j]<0) break;
            sub.push_back(c[j]);
            bc(c,t-c[j],j+1);
            sub.pop_back();
        }
    }
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        bc(candidates, target, 0);
        return res;
    }
};