C中十六进制到二进制的转换显示错误的输出

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

int is_valid_hex(const char *str) {
    for (int i = 0; str[i] != '\0'; i++) {
        if (!isxdigit(str[i])) {
            return 0;
        }
    }
    return 1;
}

void hex_to_binary(const char *hex_str) {
    if (!is_valid_hex(hex_str)) {
        printf("Invalid hexadecimal input.\n");
        return;
    }

    unsigned int num = strtoul(hex_str, NULL, 16);
    for (int i = sizeof(num) * 8 - 1; i >= 0; i--) {
        printf("%d", (num >> i) & 1);
    }
    printf("\n");
}

int main() {
    const char *hex_input = "1A3F";
    hex_to_binary(hex_input);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>

void hex_to_binary_large(const char *hex_str) {
    unsigned long long num = strtoull(hex_str, NULL, 16);
    for (int i = sizeof(num) * 8 - 1; i >= 0; i--) {
        printf("%d", (num >> i) & 1);
    }
    printf("\n");
}

int main() {
    const char *large_hex_input = "FFFFFFFFFFFFFFFF"; // 64-bit number
    hex_to_binary_large(large_hex_input);
    return 0;
}

void formatted_hex_to_binary(const char *hex_str, int bit_width) {
    unsigned int num = strtoul(hex_str, NULL, 16);
    for (int i = bit_width - 1; i >= 0; i--) {
        printf("%d", (num >> i) & 1);
    }
    printf("\n");
}

int main() {
    const char *formatted_hex_input = "1A";
    formatted_hex_to_binary(formatted_hex_input, 8); // Ensure 8-bit output
    return 0;
}