题解 | #24点游戏算法#

每次都从nums[0]开始竟然也可以过

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int[] nums = new int[4];
            for (int i = 0; i < 4; i++) {
                nums[i] = in.nextInt();
            }
            boolean[] v = new boolean[4];
            System.out.println(backtrack(nums, v, nums[0]));
        }
    }

    private static boolean backtrack(int[] nums, boolean[] visited, double res) {
        if (res == 24) {
            return true;
        }
        for (int i = 1; i < nums.length; i++) {
            if (!visited[i]) {
                visited[i] = true;
                if (backtrack(nums, visited, res + nums[i]) ||
                        backtrack(nums, visited, res - nums[i]) ||
                        backtrack(nums, visited, res * nums[i]) ||
                        backtrack(nums, visited, res / nums[i])) {
                    return true;
                }
                visited[i] = false;
            }
        }
        return false;
    }
}