题目

题解

代码

import java.util.*;

public class code77 {

    public static List<List<Integer>> combine(int n, int k) {
        List<List<Integer>> res = new ArrayList<List<Integer>>();
        if (n <= 0 || k <= 0 || n < k) {
            return res;
        }
        List<Integer> list = new ArrayList<Integer>();
        dfs(res, list, 0, 1, n, k);
        return res;
    }

    public static void dfs(List<List<Integer>> res, List<Integer> list, int count, int start, int n, int k) {
        if (count == k) {
            res.add(new ArrayList<>(list));
            return;
        }
        for (int i = start; i <= n - (k - list.size()) + 1; i++) {
            list.add(i);
            dfs(res, list, count + 1, i + 1, n, k);
            list.remove(list.size() - 1);
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNextInt()) {
            int n = sc.nextInt();
            int k = sc.nextInt();
            List<List<Integer>> res = combine(n, k);
            System.out.println(res);
        }
        sc.close();
    }
}
77. 组合

题目

题解

代码

参考
