标签：style blog http color os io
Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.
For example,
If n = 4 and k = 2, a solution is:[ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ]
算法：
思路1： 迭代，k个数就用k层迭代。貌似实现起来也是略有难度的
思路2： DFS，不啰嗦
1 public class Solution { 2 List<List<Integer>> result = new ArrayList<List<Integer>>(); 3 public List<List<Integer>> combine(int n, int k) { 4 if(n < k || k < 0 || n < 0) return result; 5 List<Integer> list = new ArrayList<Integer>(); 6 dfs(list,1, n, k); 7 return result; 8 } 9 private void dfs(List<Integer> list,int start,int n,int left){ 10 if(left == 0){ 11 result.add(new ArrayList<Integer>(list)); 12 return ; 13 } 14 for(int i = start; i <= n ; i++){ 15 list.add(i); 16 dfs(list, i + 1, n, left - 1); 17 list.remove(list.size() - 1); 18 } 19 } 20 }
[leetcode]Combinations,布布扣,bubuko.com
标签：style blog http color os io
原文地址：http://www.cnblogs.com/huntfor/p/3860695.html
