Submission

Score: 100

User: lingusso

Problemset: บวกเลขฐาน

Language: c

Time: 0.002 second

Submitted On: 2025-10-12 13:57:53

#include <stdio.h>
#include <string.h>
#include <ctype.h> // For toupper or similar if needed, though not strictly required here

// Function to convert a base-B number string to its decimal (base-10) value
long long base_to_decimal(const char* num_str, int base) {
    long long decimal_value = 0;
    int len = strlen(num_str);

    for (int i = 0; i < len; i++) {
        int digit_value;
        char c = num_str[i];

        if (c >= '0' && c <= '9') {
            digit_value = c - '0';
        } else if (c >= 'A' && c <= 'Z') {
            // For digits > 9, like 'A'=10, 'B'=11, etc.
            digit_value = c - 'A' + 10;
        } else if (c >= 'a' && c <= 'z') {
            // Optional: Handle lowercase letters if needed
            digit_value = c - 'a' + 10;
        } else {
            // Invalid character
            continue;
        }

        // Check if the digit is valid for the given base
        if (digit_value >= base) {
            fprintf(stderr, "Error: Digit %c is invalid for base %d.\n", c, base);
            return -1; // Return error value
        }

        // Conversion core logic: decimal = decimal * base + digit_value
        decimal_value = decimal_value * base + digit_value;
    }
    return decimal_value;
}

// Function to convert a decimal number to a base-B string and print it
void decimal_to_base(long long sum, int base) {
    if (sum == 0) {
        printf("0\n");
        return;
    }

    // Using an int array to store digit values (0-B-1)
    int output_digits[40];
    int r = 0;

    while (sum > 0) {
        int remainder = sum % base;
        output_digits[r] = remainder;
        sum /= base;
        r++;
    }

    // Print the digits in REVERSE order (from most significant to least significant)
    for (int i = r - 1; i >= 0; i--) {
        int digit_value = output_digits[i];

        if (digit_value > 9) {
            // Convert 10 -> 'A', 11 -> 'B', etc.
            // ASCII of 'A' is 65. 'A' - 10 = 55. This is equivalent to your original 'digit_value + 55'
            printf("%c", digit_value + 'A' - 10);
        } else {
            // Convert 0 -> '0', 1 -> '1', etc.
            // ASCII of '0' is 48. This is equivalent to your original 'digit_value + 48'
            printf("%c", digit_value + '0');
        }
    }
    printf("\n"); // Add a newline at the end
}


int main() {
    int n; // n is the base B
    if (scanf("%d", &n) != 1) {
        return 1; // Handle read error
    }
    // Check for valid base (e.g., base 2 to 36)
    if (n < 2 || n > 36) {
        fprintf(stderr, "Error: Base must be between 2 and 36.\n");
        return 1;
    }

    char num1[40], num2[40];
    if (scanf("%39s", num1) != 1 || scanf("%39s", num2) != 1) {
        return 1; // Handle read error
    }

    // Convert both numbers to decimal
    long long decinum1 = base_to_decimal(num1, n);
    long long decinum2 = base_to_decimal(num2, n);
    
    // Check if conversion failed
    if (decinum1 == -1 || decinum2 == -1) {
        return 1;
    }

    // Add the numbers in decimal
    long long sum = decinum1 + decinum2;

    // Convert the sum back to base n and print
    decimal_to_base(sum, n);

    return 0;
}