将16进制数转换为2进制c语言

以下是将16进制数转换为2进制的c语言代码：

#include <stdio.h>

int main()
{
    char hex[17];
    long long bin, place;
    int i = 0, rem, val;

    printf("请输入一个16进制数: ");
    scanf("%s", hex);

    bin = 0ll;
    place = 0ll;

    // 将每个16进制数位转换为2进制
    for (i = 0; hex[i] != '\0'; i++)
    {
        bin = bin * place;

        switch (hex[i])
        {
            case '0':
                val = 0;
                break;
            case '1':
                val = 1;
                break;
            case '2':
                val = 2;
                break;
            case '3':
                val = 3;
                break;
            case '4':
                val = 4;
                break;
            case '5':
                val = 5;
                break;
            case '6':
                val = 6;
                break;
            case '7':
                val = 7;
                break;
            case '8':
                val = 8;
                break;
            case '9':
                val = 9;
                break;
            case 'a':
            case 'A':
                val = 10;
                break;
            case 'b':
            case 'B':
                val = 11;
                break;
            case 'c':
            case 'C':
                val = 12;
                break;
            case 'd':
            case 'D':
                val = 13;
                break;
            case 'e':
            case 'E':
                val = 14;
                break;
            case 'f':
            case 'F':
                val = 15;
                break;
            default:
                printf("无效的输入\n");
                return 1;
        }

        bin += val;
        place = 10ll;
    }

    // 将2进制数转换为16进制
    i = 0;
    while (bin != 0)
    {
        rem = bin % 2;
        bin /= 2;
        hex[i] = rem == 0 ? '0' : '1';
        i++;
    }
    hex[i] = '\0';

    // 输出2进制数
    printf("2进制数为: ");
    for (i = i - 1; i >= 0; i--)
        printf("%c", hex[i]);
    printf("\n");

    return 0;
}

该程序接受用户输入一个16进制数，并将其转换为2进制数。