Number to Roman in C Language

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

char* intToRoman(int num) {
    static const int values[] = {
        1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1
    };
    static const char* symbols[] = {
        "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"
    };

    char* result = (char*)malloc(16 * sizeof(char));
    if (!result) return NULL;
    result[0] = '';

    for (int i = 0; i < 13 && num > 0; i++) {
        while (num >= values[i]) {
            strcat(result, symbols[i]);
            num -= values[i];
        }
    }

    return result;
}

int main(void) {
    int testNum = 1994;
    char* roman = intToRoman(testNum);
    printf("%d in Roman is: %s
", testNum, roman);
    free(roman);
    return 0;
}

2. Reverse C Function: romanToInt()

For bidirectional support, here is the companion C lookahead parser:

int charToValue(char c) {
    switch(c) {
        case 'I': return 1;
        case 'V': return 5;
        case 'X': return 10;
        case 'L': return 50;
        case 'C': return 100;
        case 'D': return 500;
        case 'M': return 1000;
        default: return 0;
    }
}

int romanToInt(const char* s) {
    int total = 0;
    int len = strlen(s);

    for (int i = 0; i < len; i++) {
        int current = charToValue(s[i]);
        int next = (i + 1 < len) ? charToValue(s[i + 1]) : 0;

        if (current < next) {
            total -= current;
        } else {
            total += current;
        }
    }

    return total;
}