当整数长度未知时，保持前导零

问题描述

以下程序将反转用户输入.但是，对于带有尾随零的数字，在打印反向数字时，零将被忽略".

The following program reverses user input. However, for numbers with trailing zeroes, the zeroes are 'ignored' when printing the reversed number.

#include<stdio.h>

int main(void)
{
   int n, reversedNumber = 0, remainder;

    printf("Enter an integer: ");
    scanf("%d", &n);

    while(n != 0)
    {
        remainder = n%10;
        reversedNumber = reversedNumber*10 + remainder;
        n /= 10;
    }

    printf("Reversed Number = %d\n", reversedNumber);

    return 0;
}

由于用户输入的整数长度未知，我们如何打印所有尾随的零，例如:

Since the integer length of the user input is unknown, how can we print all the trailing zeros for example:

Enter an Integer: 3000
Reversed Number = 0003

推荐答案

不是.:-)

计算迭代次数，并将其作为宽度传递给对 printf 的最终调用.

Count the number of iterations and pass it to the final call to printf as width.

#include<stdio.h>

int main(void)
{
   int n, reversedNumber = 0, remainder;

   printf("Enter an integer: ");
   scanf("%d", &n);

   {
     size_t i = (0 > n);

     while (n != 0)
     {
       remainder = n % 10;
       reversedNumber = reversedNumber * 10 + remainder;
       n /= 10;
       ++i;
     }

     printf("Reversed Number = %0*d\n", (int) i, reversedNumber); /* Alternatively
                                            to the cast you can define i as int. */
   }

   return 0;
}

从文档:

[...]

• 可选的最小字段宽度.如果转换后的值的字符数少于字段宽度，则在字段宽度的左边(或默认情况下，如果给定了左边的调整标志，则在右边)用空格填充(默认情况下).字段宽度采用星号*(稍后描述)或非负十进制整数的形式.[...])

[...]

5 如上所述，字段宽度可以用星号表示.在这种情况下，int参数可提供字段宽度或精度.指定字段宽度[...]的参数应(按此顺序)出现在要转换的参数(如果有)之前.

5 As noted above, a field width [...] may be indicated by an asterisk. In this case, an int argument supplies the field width or precision. The arguments specifying field width [...] shall appear (in that order) before the argument (if any) to be converted.

[...]

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