#include <stdio.h>
#include <string.h>
#include <stdbool.h>

// Function to check if input contains only '0' and '1'
bool isValidBinary(const char *binary) {
    int length = strlen(binary);
    for (int i = 0; i < length; i++) {
        if (binary[i] != '0' && binary[i] != '1') {
            return false; // Return false if any character is not '0' or '1'
        }
    }
    return true; // Return true if all characters are '0' or '1'
}


// Function to convert binary number to decimal
int bin2dec(const char *binary) {
    int length = strlen(binary); // Calculate the length of the binary string
    int decimal = 0;
    int power = 1; // Power of two

    for (int i = length - 1; i >= 0; i--) {
        if (binary[i] == '1') {
            decimal += power; // Add to the decimal value if the bit is '1'
        }
        power *= 2; // Increase the power of two for the next bit (power is ... multiplication)
    }

    return decimal;
}

int main() {
    char binary[32];
    printf("Enter a binary number to convert to decimal: ");
    scanf("%s", binary);

    if (!isValidBinary(binary)) {
        printf("Invalid input! The input should contain only '0' and '1'.\n");
        return 1; // Exit the program with an error code
    }
    int decimal = bin2dec(binary);
    printf("Decimal equivalent: %d\n", decimal);

    return 0;
}