0040. Combination Sum II
https://leetcode.com/problems/combination-sum-ii
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:**
[
[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
ac
class Solution {
public List<List<Integer>> combinationSum2(int[] candidates, int target) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
Arrays.sort(candidates);
backtrack(candidates, 0, target, res, new ArrayList<Integer>());
return res;
}
private void backtrack(int[] candidates, int start, int remain, List<List<Integer>> res, List<Integer> note) {
// exit
if (remain < 0) return;
if (remain == 0) {
res.add(new ArrayList<Integer>(note));
return;
}
for (int i = start; i < candidates.length; i++) {
if (i > start && candidates[i] == candidates[i-1]) continue; // skip duplicates, only take start point value
note.add(candidates[i]);
backtrack(candidates, i+1, remain-candidates[i], res, note);
note.remove(note.size()-1);
}
}
}
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