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Leetcode040-combinationSumII

Posted on Edited on In Views: Valine:
Solution Report of LeetCode Acceptted

Description

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

Each number in candidates may only be used once in the combination.

Note:

  • All numbers (including target) will be positive integers.
  • The solution set must not contain duplicate combinations.

Example

Example 1:

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Input: candidates = [10,1,2,7,6,1,5], target = 8,
A solution set is:
[
  [1, 7],
  [1, 2, 5],
  [2, 6],
  [1, 1, 6]
]

Example 2:
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Input: candidates = [2,5,2,1,2], target = 5,
A solution set is:
[
  [1,2,2],
  [5]
]

Solution

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class Solution {
    public void backtracking(List<List<Integer>> res, List<Integer> tmp, int[] nums, int target, int start, int sum){
        if (sum == target){
            res.add(new ArrayList<>(tmp));
            return;
        } 
        for (int i = start; i < nums.length; i++){
            if (i > start && nums[i] == nums[i-1]) continue;
            tmp.add(nums[i]);
            if (sum + nums[i] <= target) backtracking(res, tmp, nums, target, i + 1, sum + nums[i]);
            else {
                tmp.remove(tmp.size()-1);
                return;
            }
            tmp.remove(tmp.size() - 1);
        }
    }
    
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        List<List<Integer>> res = new ArrayList<>();
        if (candidates == null) return res;
        Arrays.sort(candidates);
        backtracking(res, new ArrayList<Integer>(), candidates, target, 0, 0);
        return res;
    }
}