题目1 : The Lastest Time

时间限制:10000ms

单点时限:1000ms

内存限制:256MB

描述

What is latest time you can make with 4 digits A, B, C and D?

For example if the 4 digits are 1, 0, 0, 0, you can make 4 times with them: 00:01, 00:10, 01:00, 10:00. The lastest time will be 10:00. Note a valid time is between 00:00 and 23:59.

输入

One line with 4 digits A, B, C and D, separated by a space. (0 <= A, B, C, D <= 9)

输出

Output the lastest time in the format "hh:mm". If there is no valid time output NOT POSSIBLE.  

样例输入

0 9 0 0

样例输出

09:00

import java.util.Scanner;

public class Main_207 {
    private static int[] maxTime =  new int[]{0,0,0,0};
    private  static boolean hasValidate= false;

    public static  void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int[] nums = new int[4];
        for(int i = 0; i < 4; i ++){
            nums[i] = sc.nextInt();
        }
        System.out.println(solve(nums));
        sc.close();
    }
    public static String solve(int[] nums){
        permute(nums, 0);
        if(hasValidate){
            return String.format("%d%d:%d%d", maxTime[0],maxTime[1], maxTime[2],maxTime[3]);
        }else
            return "NOT POSSBLE";

    }

    public static void permute(int []nums, int start){
        if(start == 4){
            if(!isValid(nums)){
                return ;
            }
            hasValidate = true;
            if(lessTo(maxTime , nums)){
                System.arraycopy(nums,0,maxTime, 0 ,nums.length);
            }
        }
        for(int i = start ; i < 4; i++){
            swap(nums,start,i);
            permute(nums, start+1);
            swap(nums,start,i);
        }
    }
    public static void swap(int[]a, int i, int j){
        if(i == j ) return ;
        int t = a[i];
        a[i] = a[j];
        a[j] = t;
    }
    public static boolean isValid(int []time){
        int hh = time[0] * 10 + time[1];
        int mm = time[2] * 10 + time[3];
        if(hh < 24 && mm < 60){
            return true;
        }else{
            return false;
        }
    }
    public static boolean lessTo(int[]t1, int[]t2){
        int m1= (t1[0] * 10 + t1[1]) * 60 + t1[2]* 10 + t1[3];
        int m2 = (t2[0] * 10 + t2[1]) * 60 + t2[2]* 10 + t2[3];
        if(m1 < m2){
            return true;
        }
        return  false;
    }
}