通过c语言将16进制转为2进制

以下是将16进制数转换为2进制数的C语言程序：

#include <stdio.h>

int main() {
    char hex[17];
    long long binary = 0;
    int i = 0;

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

    // 将16进制数转换为2进制数
    while (hex[i]) {
        switch (hex[i]) {
            case '0':
                binary = binary * 16 + 0; break;
            case '1':
                binary = binary * 16 + 1; break;
            case '2':
                binary = binary * 16 + 10; break;
            case '3':
                binary = binary * 16 + 11; break;
            case '4':
                binary = binary * 16 + 100; break;
            case '5':
                binary = binary * 16 + 101; break;
            case '6':
                binary = binary * 16 + 110; break;
            case '7':
                binary = binary * 16 + 111; break;
            case '8':
                binary = binary * 16 + 1000; break;
            case '9':
                binary = binary * 16 + 1001; break;
            case 'A':
            case 'a':
                binary = binary * 16 + 1010; break;
            case 'B':
            case 'b':
                binary = binary * 16 + 1011; break;
            case 'C':
            case 'c':
                binary = binary * 16 + 1100; break;
            case 'D':
            case 'd':
                binary = binary * 16 + 1101; break;
            case 'E':
            case 'e':
                binary = binary * 16 + 1110; break;
            case 'F':
            case 'f':
                binary = binary * 16 + 1111; break;
            default:
                printf("非法输入！\n");
                return 1;
        }
        i++;
    }

    printf("转换为2进制数为: %lld\n", binary);

    return 0;
}

程序通过 `scanf()` 函数获取一个16进制数，然后通过 `while` 循环将其转换为2进制数。在循环中，我们使用 `switch` 语句将每个16进制数转换为对应的4位2进制数。最后，用 `printf()` 输出结果。