Roman to Integer Conversion in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Roman to Integer Conversion Function

What is the output of the following C code when the input Roman numeral is "MCMXCIV"?

DSA C

int romanToInt(char * s) {
    int map[26] = {0};
    map['I' - 'A'] = 1;
    map['V' - 'A'] = 5;
    map['X' - 'A'] = 10;
    map['L' - 'A'] = 50;
    map['C' - 'A'] = 100;
    map['D' - 'A'] = 500;
    map['M' - 'A'] = 1000;

    int total = 0;
    int i = 0;
    while (s[i]) {
        int value = map[s[i] - 'A'];
        int nextValue = map[s[i+1] - 'A'];
        if (nextValue > value) {
            total += (nextValue - value);
            i += 2;
        } else {
            total += value;
            i++;
        }
    }
    return total;
}

int main() {
    char roman[] = "MCMXCIV";
    int result = romanToInt(roman);
    printf("%d\n", result);
    return 0;
}

A 1994

B 1094

C 1949

D None of the above

💡 Hint

Remember that when a smaller value precedes a larger value, you subtract the smaller from the larger.

The Roman numeral MCMXCIV is converted as follows: M (1000) + CM (900) + XC (90) + IV (4) = 1994.

❓ Predict Output

intermediate

Output of Roman to Integer Conversion with Repeated Numerals

What is the output of the following C code when the input Roman numeral is "III"?

DSA C

int romanToInt(char * s) {
    int map[26] = {0};
    map['I' - 'A'] = 1;
    map['V' - 'A'] = 5;
    map['X' - 'A'] = 10;
    map['L' - 'A'] = 50;
    map['C' - 'A'] = 100;
    map['D' - 'A'] = 500;
    map['M' - 'A'] = 1000;

    int total = 0;
    int i = 0;
    while (s[i]) {
        int value = map[s[i] - 'A'];
        int nextValue = map[s[i+1] - 'A'];
        if (nextValue > value) {
            total += (nextValue - value);
            i += 2;
        } else {
            total += value;
            i++;
        }
    }
    return total;
}

int main() {
    char roman[] = "III";
    int result = romanToInt(roman);
    printf("%d\n", result);
    return 0;
}

A 6

B 3

C 1

D 0

💡 Hint

Repeated numerals add their values.

Each 'I' is 1, so III = 1 + 1 + 1 = 3.

🔧 Debug

advanced

Identify the Error in Roman to Integer Conversion Code

What error will the following C code produce when run with input "VI"?

DSA C

int romanToInt(char * s) {
    int map[26] = {0};
    map['I' - 'A'] = 1;
    map['V' - 'A'] = 5;
    map['X' - 'A'] = 10;
    map['L' - 'A'] = 50;
    map['C' - 'A'] = 100;
    map['D' - 'A'] = 500;
    map['M' - 'A'] = 1000;

    int total = 0;
    int i = 0;
    while (s[i]) {
        int value = map[s[i] - 'A'];
        int nextValue = map[s[i+1] - 'A'];
        if (nextValue > value) {
            total += (nextValue - value);
            i += 2;
        } else {
            total += value;
            i++;
        }
    }
    return total;
}

int main() {
    char roman[] = "VI";
    int result = romanToInt(roman);
    printf("%d\n", result);
    return 0;
}

A Segmentation fault due to accessing s[i+1] when i+1 is out of bounds

B Prints 4 correctly

C Prints 6 incorrectly

D Compilation error due to missing header

💡 Hint

Check how the code accesses s[i+1] without verifying if it exists.

When i is at the last character, s[i+1] is out of bounds, causing undefined behavior or segmentation fault.

❓ Predict Output

advanced

Output of Roman to Integer Conversion with Mixed Numerals

What is the output of the following C code when the input Roman numeral is "XLII"?

DSA C

int romanToInt(char * s) {
    int map[26] = {0};
    map['I' - 'A'] = 1;
    map['V' - 'A'] = 5;
    map['X' - 'A'] = 10;
    map['L' - 'A'] = 50;
    map['C' - 'A'] = 100;
    map['D' - 'A'] = 500;
    map['M' - 'A'] = 1000;

    int total = 0;
    int i = 0;
    while (s[i]) {
        int value = map[s[i] - 'A'];
        int nextValue = map[s[i+1] - 'A'];
        if (nextValue > value) {
            total += (nextValue - value);
            i += 2;
        } else {
            total += value;
            i++;
        }
    }
    return total;
}

int main() {
    char roman[] = "XLII";
    int result = romanToInt(roman);
    printf("%d\n", result);
    return 0;
}

A 44

B 52

C 40

D 42

💡 Hint

XL is 40, II is 2, sum them.

XL is 50 - 10 = 40, plus II (1 + 1) = 2, total 42.

🧠 Conceptual

expert

Why does the Roman to Integer Conversion Algorithm Check Next Character?

Why does the Roman to Integer conversion algorithm check the next character's value when processing the current character?

A To skip invalid characters in the input string

B To convert the Roman numeral to lowercase before processing

C To decide whether to add or subtract the current numeral's value based on Roman numeral rules

D To count the total number of characters in the string

💡 Hint

Roman numerals use subtractive notation when a smaller numeral precedes a larger one.

If the next numeral is larger, the current numeral's value is subtracted; otherwise, it is added.