c - 在 C 编程中，如何用左侧的 0 填充我的二进制文件？

Question

你们知道如何在我的二进制文件左边填充 0 吗？我的职能是:

void PrintBinaryUpTo(int n)
{
    int i;
    char string [11];
    for(i = 1; i <= n; i++)
    {
        itoa(i, string, 2);

        printf("%d in binary is: %s\n", i, string);
    }
}

它返回:

1 in binary is: 1
2 in binary is: 10
3 in binary is: 11

但我希望它是这样的:

1 in binary is: 0000000001
2 in binary is: 0000000010
3 in binary is: 0000000011

编辑:我是这样做的，但我很确定有更聪明的方法可以做到这一点。

void PrintBinaryUpTo(int n)
{
    int i;
    char string [11];
    char result[11];
    for(i = 1; i <= n; i++)
    {
        itoa(i, string, 2);

        switch(strlen(string))
        {
            case 1:
            strcpy(result, "000000000");
            strcat(result, string);
            break;

            case 2:
            strcpy(result, "00000000");
            strcat(result, string);
            break;

            case 3:
            strcpy(result, "0000000");
            strcat(result, string);
            break;

            case 4:
            strcpy(result, "000000");
            strcat(result, string);
            break;

            case 5:
            strcpy(result, "00000");
            strcat(result, string);
            break;

            case 6:
            strcpy(result, "0000");
            strcat(result, string);
            break;

            case 7:
            strcpy(result, "000");
            strcat(result, string);
            break;

            case 8:
            strcpy(result, "00");
            strcat(result, string);
            break;

            case 9:
            strcpy(result, "0");
            strcat(result, string);
            break;

            default:
            strcpy(result, string);
            break;
        }
        printf("%d in binary is: %s\n", i, result);
    }
}

输出:

1 in binary is: 0000000001
2 in binary is: 0000000010
3 in binary is: 0000000011
4 in binary is: 0000000100
5 in binary is: 0000000101
6 in binary is: 0000000110
7 in binary is: 0000000111
8 in binary is: 0000001000
9 in binary is: 0000001001

Answer 1

不，除非您定义自己的 itoa 函数，否则实际上没有任何方法可以做到这一点。
然而，有一种可移植的方法来简化您的功能:

void PrintBinaryUpTo(int n)
{
    int i;
    char string[11];
    char result[11];
    char *zeroes = "000000000";
    for(i = 1; i <= n; i++)
    {
        itoa(i, string, 2);
        /* Buffer the number to 10 digits */
        strcpy(result, zeroes+strlen(string)-1);
        strcat(result, string);
        printf("%d in binary is: %s\n", i, result);
    }
}

这不需要您拥有的整个 switch case 东西。

另一种不可移植的方法(需要 MSVC)是使用 %010s 格式说明符，它用零填充:

void PrintBinaryUpTo(int n)
{
    int i;
    char string[11];
    for(i = 1; i <= n; i++)
    {
        itoa(i, string, 2);
        /* Buffer the number to 10 digits with %010s */
        printf("%d in binary is: %010s\n", i, string);
    }
}