40. Combination Sum II

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40. Combination Sum II

Description

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

Each number in candidatesmay only be used once in the combination.

Note: The solution set must not contain duplicate combinations.

Example 1:

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

Example 2:

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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

Hints/Notes

  • 2024/12/19
  • backtracking
  • review together with 3sum
  • No solution from 0x3F

Solution

Language: C++

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class Solution {
public:
    vector<int> cur;
    vector<vector<int>> res;

    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        dfs(candidates, 0, target);
        return res;
    }

    void dfs(vector<int>& candidates, int start, int target) {
        if (target == 0) {
            res.push_back(cur);
            return;
        }
        if (target < 0 || start == candidates.size()) {
            return;
        }
        for (int i = start; i < candidates.size(); i++) {
            if (i > start && candidates[i] == candidates[i - 1]) {
                continue;
            }
            if (candidates[i] > target) {
                break;
            }
            cur.push_back(candidates[i]);
            dfs(candidates, i + 1, target - candidates[i]);
            cur.pop_back();
        }
    }
};