package jjn.carl.backtrack;
import java.util.ArrayList;import java.util.List;
/** * @author Jiang Jining * @since 2023-07-23 21:40 */public class LeetCode77 {    public List<List<Integer>> combine(int n, int k) {        List<List<Integer>> result = new ArrayList<>();        backtrack(1, n, k, result, new ArrayList<>());        return result;    }        private void backtrack(int startIndex, int n, int k, List<List<Integer>> result, List<Integer> path) {        if (path.size() == k) {            result.add(new ArrayList<>(path));            return;        }        for (int i = startIndex; i <= n - (k - path.size()) + 1; i++) {            path.add(i);            backtrack(i + 1, n, k, result, path);            path.remove(path.size() - 1);        }    }        public static void main(String[] args) {        System.out.println("new LeetCode77().combine(4,2) = " + new LeetCode77().combine(4, 2));    }}