程序代码：

#include <locale.h>
#include <stdio.h>
#include <conio.h>

void rhombus(size_t width);

void main(void)
{
    size_t number;

    setlocale(LC_ALL, "chs");        // 设定语言为中文输出

    do
    {
        wprintf_s(L"\n菱形底宽(0-20, 0结束程序): ");
        scanf_s("%d", &number);
        if (number > 0 && number <= 20)
        {
            rhombus(number);
        }
    } while (number > 0);
}

void rhombus(size_t width)
{
    const char character('*');
    const char blank(' ');
    size_t i, j, k;
    int number;

    if (width % 2 == 0)
    {
        width++;
    }
    number = -1;
    for (i = 1; i <= width; i++)
    {
        if (i <= width / 2 + 1)
        {
            number += 2;
        }
        else
        {
            number -= 2;
        }
        for (j = 1; j <= (width - number) / 2; j++)
        {
            putch(blank);
        }
        for (k = 1; k <= number; k++)
        {
            putch(character);
        }
        putch('\n');
    }
}