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Combination Sum II⚓︎

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Description⚓︎

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:
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[
[1,1,6],
[1,2,5],
[1,7],
[2,6]
]

Example 2:

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

Constraints:

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

Solution⚓︎

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class Solution {
private:
    vector<vector<int>> res;
    vector<int> path;
    void backtracking(vector<int>& candidates, int sum, int startIndex) {
        // if (sum < 0) return;
        if (sum == 0) {
            res.push_back(path);
            return;
        }
        for (int i = startIndex; i < candidates.size() && sum - candidates[i] >= 0; i++) {
            if (i != startIndex && candidates[i] == candidates[i - 1]) continue;
            path.push_back(candidates[i]);
            backtracking(candidates, sum - candidates[i], i + 1);
            path.pop_back();
        }
    }
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        backtracking(candidates, target, 0);
        return res;
    }
};