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leetcode no 40 combination sum ii

admin 11月 11, 2020 0

1. 题目

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

Each number in C 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.
For example, given candidate set [10, 1, 2, 7, 6, 1, 5] and target 8,
A solution set is:
[
[1, 7],
[1, 2, 5],
[2, 6],
[1, 1, 6]
]

2. 思路

同上一题一样，也是采用回溯法

public class  {
   	public List<List<Integer>> combinationSum2(int[] candidates, int target) {
       	List<List<Integer>> result = new LinkedList<List<Integer>>();
       	List<Integer> tmp = new LinkedList<Integer>();
       	Arrays.sort(candidates);
       	dfs(candidates, target, 0, result, tmp);
       	return result;
   	}
	public void dfs(int[] candidates, int target, int index, List<List<Integer>> result, List<Integer> tmp){
		if (target == 0) {  
           	result.add(new ArrayList<Integer>(tmp));  
       	}  
       	for (int i = index; i < candidates.length && candidates[i] <= target; i++) {  
           	if (i > index && candidates[i] == candidates[i - 1]) continue;   
           	tmp.add(candidates[i]);  
           	dfs(candidates, target - candidates[i], i + 1, result, tmp);  
           	tmp.remove(tmp.size() - 1); 
       	}
   	}  
	
}