*[Lintcode]k Sum II

来源：互联网发布：淘宝文案策划待遇编辑：程序博客网时间：2024/06/06 13:33

Given n unique integers, number k (1<=k<=n) and target.

Find all possible k integers where their sum is target.

Example

Given [1,2,3,4], k = 2, target = 5. Return:

[  [1,4],  [2,3]]

分析：递归

public class Solution {    /**     * @param A: an integer array.     * @param k: a positive integer (k <= length(A))     * @param target: a integer     * @return a list of lists of integer      */     public ArrayList<ArrayList<Integer>> kSumII(int[] A, int k, int target) {        ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();        helper(A, k, target, 0, res, new ArrayList<Integer>());        return res;    }        void helper(int[] A, int k, int target, int index, ArrayList<ArrayList<Integer>> res, ArrayList<Integer> list) {        if(target == 0 && k == 0) {            res.add(new ArrayList<Integer>(list));            return;        }        if(index >= A.length || target < 0 || k < 0) return;        for(int i = index; i < A.length; i++) {            list.add(A[i]);            helper(A, k - 1, target - A[i], i + 1, res, list);            list.remove(list.size() - 1);        }    }}

0 0