40. Combination Sum II

避免这个循环的重复 所以i>position && nums[i] == nums[i-1]

 

 

class Solution {
    List<List<Integer>> res = new ArrayList<>();
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        Arrays.sort(candidates);
        backtrack(candidates, target, 0, new ArrayList<>(), 0);
        return res;
    }
    
    public void backtrack(int[] candidates, int target, int sum, List<Integer> list, int position) {
        if(sum > target) return;
        if(sum == target) {
            res.add(new ArrayList<>(list));
        }
        for(int i = position; i < candidates.length; i++) {
            if(i > position && candidates[i] == candidates[i-1]) { //注意 i > position
                continue;
            }
            list.add(candidates[i]);
            sum += candidates[i];
            backtrack(candidates, target, sum, list, i+1);
            list.remove(list.size() - 1);
            sum -= candidates[i];
        }
    }
}