java LintCode 90.k数和(二)_算法 k个数之和 java

1.题目

2.解法
①一维数组+dfs

public class Solution {
    public List<List<Integer>> kSumII(int[] A, int k, int target) {
        List<List<Integer>> res = new ArrayList<>();
        List<Integer> temp = new ArrayList<>();
        int n = A.length;
        dfs(0, k, n, A, target, res, temp);
        return res;
    }
    private void dfs(int start, int k, int n, int[] A, int target, List<List<Integer>> res, List<Integer> temp){
        if(k == 0 && target == 0){
            res.add(new ArrayList<>(temp));
            return;
        }
        for(int i = start; i < n; i++){
            temp.add(A[i]);
            dfs(i + 1, k - 1, n, A, target - A[i], res, temp);
            temp.remove(temp.size() - 1);
        }
    }
}
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