Java中的汽车加油问题.任何人都可以找出while循环条件中的任何错误吗? [英] Car fueling problem in java. Can anyone figure out any error in while loop condition?

问题描述

import java.util.*;
import java.io.*;

public class CarFueling {
 static int compute_refills(int dist,int tank,int stops[],int n){
    
        int current_refills=0;
        int num_refills=0;
        int last_refill=0;
        while(current_refills<=n) {
             last_refill = current_refills;
            while ((current_refills <= n) && (stops[current_refills + 1] - stops[last_refill]) <= tank) {
                current_refills = current_refills + 1;
            }

            if (current_refills == last_refill)
                return -1;
            if (current_refills <= n)
                num_refills = num_refills + 1;


        }
        return num_refills;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int dist = scanner.nextInt();
        int tank = scanner.nextInt();
       int n = scanner.nextInt();
        int stops[] = new int[n*n*n];// to solve array index out of bound exception increase the size of the array
        for (int i = 0; i < n; i++) {
            stops[i] = scanner.nextInt();
        }

       System.out.println(compute_refills(dist,tank,stops,n));

    }
}

我认为while循环条件存在一些问题.
输入:
950400
4
200375550750
我的输出:
1
正确的输出:
2

I think there is some issue in my while loop condition.
Input:
950 400
4
200 375 550 750
my output:
1
correct output:
2

推荐答案

如果您看

(current_refills <= n) && (stops[current_refills + 1] ... )

部分，两件事:

• current_refills< = n 对于 n-1 (n元素数组的最后一个元素，因为第一个元素的索引为0)都是正确的，并且 n (已在数组外部)
• 然后 stops [current_refills + 1] 访问元素以后"，这是这两种情况下最大值的1或2个元素

• current_refills <= n is true for both n-1 (the last element of a n-element array, as the first one has index 0), and n (which is already outside the array)
• then stops[current_refills + 1] accesses an element "later", which is 1 or 2 elements above the max for these two cases

但是实际上这是可行的，只是您可以在旅程的开头添加0，并在结尾添加 dist :

But actually this can work, just you could add 0 for the beginning of the trip and dist as the end:

int n = scanner.nextInt();
int stops[] = new int[n+2];
stops[0] = 0; // well, it is 0 already
stops[n+1] = dist;
for (int i = 1; i <= n; i++) {
    stops[i] = scanner.nextInt();
}

然后 compute_refills()可能正常工作(尽管我尚未检查).

Then compute_refills() may work correctly (though I haven't checked).

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