Roman To Integer

                                            
class Solution {
public:
    int romanToInt(string s) {
        unordered_map<char, int> romanMap = {
            {'I', 1},
            {'V', 5},
            {'X', 10},
            {'L', 50},
            {'C', 100},
            {'D', 500},
            {'M', 1000}
        };
        
        int result = 0;
        int prevValue = 0;
        
        for (int i = s.size() - 1; i >= 0; i--) {
            int curValue = romanMap[s[i]];
            if (curValue < prevValue) {
                result -= curValue;
            } else {
                result += curValue;
            }
            prevValue = curValue;
        }
        
        return result;
    }
};

                                            
class Solution {
    public int romanToInt(String s) {
        Map<Character, Integer> map = new HashMap<>();
        map.put('I', 1);
        map.put('V', 5);
        map.put('X', 10);
        map.put('L', 50);
        map.put('C', 100);
        map.put('D', 500);
        map.put('M', 1000);
        
        int prev = 0;
        int result = 0;
        
        for (int i = s.length() - 1; i >= 0; i--) {
            int value = map.get(s.charAt(i));
            
            if (value < prev) {
                result -= value;
            } else {
                result += value;
            }
            
            prev = value;
        }
        
        return result;
    }
}

                                            
class Solution(object):
    def romanToInt(self, s):
        """
        :type s: str
        :rtype: int
        """
        roman_dict = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
        result = roman_dict[s[-1]]
        
        for i in range(len(s) - 1):
            if roman_dict[s[i]] < roman_dict[s[i + 1]]:
                result -= roman_dict[s[i]]
            else:
                result += roman_dict[s[i]]
        
        return result

                                            
int romanToInt(char* s) {
    int num = 0;
    
    for(int i = 0; s[i] != '\0'; i++) {
        if(s[i] == 'I' && (s[i+1] == 'V' || s[i+1] == 'X')) {
            num -= 1;
        } else if(s[i] == 'X' && (s[i+1] == 'L' || s[i+1] == 'C')) {
            num -= 10;
        } else if(s[i] == 'C' && (s[i+1] == 'D' || s[i+1] == 'M')) {
            num -= 100;
        } else {
            switch(s[i]) {
                case 'I': num += 1; break;
                case 'V': num += 5; break;
                case 'X': num += 10; break;
                case 'L': num += 50; break;
                case 'C': num += 100; break;
                case 'D': num += 500; break;
                case 'M': num += 1000; break;
            }
        }
    }
    
    return num;
}

                                            
public class Solution {
    public int RomanToInt(string s) {
        Dictionary<char, int> romanValues = new Dictionary<char, int>
        {
            {'I', 1},
            {'V', 5},
            {'X', 10},
            {'L', 50},
            {'C', 100},
            {'D', 500},
            {'M', 1000}
        };
        
        int result = 0;
        for (int i = 0; i < s.Length; i++)
        {
            if (i < s.Length - 1 && romanValues[s[i]] < romanValues[s[i + 1]])
            {
                result -= romanValues[s[i]];
            }
            else
            {
                result += romanValues[s[i]];
            }
        }
        
        return result;
    }
}

                                            
/**
 * @param {string} s
 * @return {number}
 */
var romanToInt = function(s) {
    const romanToIntMap = {
        'I': 1,
        'V': 5,
        'X': 10,
        'L': 50,
        'C': 100,
        'D': 500,
        'M': 1000
    };
    
    let result = 0;
    for (let i = 0; i < s.length; i++) {
        if (i < s.length - 1 && romanToIntMap[s[i]] < romanToIntMap[s[i + 1]]) {
            result -= romanToIntMap[s[i]];
        } else {
            result += romanToIntMap[s[i]];
        }
    }
    
    return result;
};

                                            
function romanToInt(s: string): number {
    const romanMap: { [key: string]: number } = {
        I: 1,
        V: 5,
        X: 10,
        L: 50,
        C: 100,
        D: 500,
        M: 1000
    };

    let result: number = 0;

    for (let i = 0; i < s.length; i++) {
        if (romanMap[s[i]] < romanMap[s[i + 1]]) {
            result += romanMap[s[i + 1]] - romanMap[s[i]];
            i++;
        } else {
            result += romanMap[s[i]];
        }
    }

    return result;
};

                                            
class Solution {
    /**
     * @param String $s
     * @return Integer
     */
    function romanToInt($s) {
        $romanToInt = [
            'I' => 1,
            'V' => 5,
            'X' => 10,
            'L' => 50,
            'C' => 100,
            'D' => 500,
            'M' => 1000
        ];
        
        $result = 0;
        
        for ($i = 0; $i < strlen($s); $i++) {
            if ($i < strlen($s) - 1 && $romanToInt[$s[$i]] < $romanToInt[$s[$i+1]]) {
                $result -= $romanToInt[$s[$i]];
            } else {
                $result += $romanToInt[$s[$i]];
            }
        }
        
        return $result;
    }
}

                                            
class Solution {
    func romanToInt(_ s: String) -> Int {
        var romanValues: [Character: Int] = [
            "I": 1,
            "V": 5,
            "X": 10,
            "L": 50,
            "C": 100,
            "D": 500,
            "M": 1000
        ]
        
        var result = 0
        var prevValue = 0
        
        for char in s {
            if let value = romanValues[char] {
                result += value
                if value > prevValue {
                    result -= 2 * prevValue
                }
                prevValue = value
            }
        }
        
        return result
    }
}

                                            
class Solution {
    fun romanToInt(s: String): Int {
        val map = hashMapOf<Char, Int>(
            'I' to 1,
            'V' to 5,
            'X' to 10,
            'L' to 50,
            'C' to 100,
            'D' to 500,
            'M' to 1000
        )
        
        var result = 0
        var prevValue = 0
        
        for (i in s.length - 1 downTo 0) {
            val value = map[s[i]]!!
            if (value < prevValue) {
                result -= value
            } else {
                result += value
            }
            prevValue = value
        }
        
        return result
    }
}

                                            
class Solution {
  int romanToInt(String s) {
    Map<String, int> romanMap = {
      'I': 1,
      'V': 5,
      'X': 10,
      'L': 50,
      'C': 100,
      'D': 500,
      'M': 1000,
    };

    int result = 0;
    int prevValue = 0;

    for (int i = s.length - 1; i >= 0; i--) {
      int value = romanMap[s[i]]!;
      if (value < prevValue) {
        result -= value;
      } else {
        result += value;
      }
      prevValue = value;
    }

    return result;
  }
}

                                            
func romanToInt(s string) int {
    romanMap := map[byte]int{
        'I': 1,
        'V': 5,
        'X': 10,
        'L': 50,
        'C': 100,
        'D': 500,
        'M': 1000,
    }
    
    result := 0
    prev := 0
    
    for i := len(s) - 1; i >= 0; i-- {
        value := romanMap[s[i]]
        
        if value < prev {
            result -= value
        } else {
            result += value
        }
        
        prev = value
    }
    
    return result
}

                                            
# @param {String} s
# @return {Integer}
def roman_to_int(s)
    roman_map = {
        "I" => 1,
        "V" => 5,
        "X" => 10,
        "L" => 50,
        "C" => 100,
        "D" => 500,
        "M" => 1000
    }
    
    result = roman_map[s[-1]]
    
    (s.length - 2).downto(0) do |i|
        if roman_map[s[i]] < roman_map[s[i + 1]]
            result -= roman_map[s[i]]
        else
            result += roman_map[s[i]]
        end
    end
    
    result
end

                                            
object Solution {
    def romanToInt(s: String): Int = {
        val map = Map('I' -> 1, 'V' -> 5, 'X' -> 10, 'L' -> 50, 'C' -> 100, 'D' -> 500, 'M' -> 1000)
        var result = 0
        var prev = 0
        for (i <- s.length - 1 to 0 by -1) {
            val curr = map(s(i))
            if (curr < prev) {
                result -= curr
            } else {
                result += curr
            }
            prev = curr
        }
        result
    }
}

                                            
impl Solution {
    pub fn roman_to_int(s: String) -> i32 {
        let mut result = 0;
        let mut prev = 0;
        let mut current = 0;
        
        for c in s.chars() {
            match c {
                'I' => current = 1,
                'V' => current = 5,
                'X' => current = 10,
                'L' => current = 50,
                'C' => current = 100,
                'D' => current = 500,
                'M' => current = 1000,
                _ => current = 0,
            }
            
            result += if current > prev { current - 2 * prev } else { current };
            prev = current;
        }
        
        result
    }
}

To solve this coding challenge, we need to convert a Roman numeral string to its corresponding integer value. The procedure for this involves understanding the rules of Roman numerals and implementing them in pseudocode form.

Explanation

Roman numerals are built using a set of symbols with corresponding integer values. The primary symbols and their values are: Symbol Value

---- -----

I 1

V 5

X 10

L 50

C 100

D 500

M 1000

Basic Idea:

Normally, Roman numerals are written from largest to smallest left to right. However, in a few cases, a smaller numeral is placed before a larger numeral to indicate subtraction.
For example:

"IV" means 4 because it’s 5 (V) - 1 (I).
"IX" means 9 because it’s 10 (X) - 1 (I).

To convert a Roman numeral to an integer, we traverse the string from left to right. If a numeral is smaller than the numeral following it, we subtract it from the total. Otherwise, we add it to the total.

Detailed Steps in Pseudocode:

First, create a dictionary to map Roman numeral symbols to their integer values.
Initialize a result variable with the value of the last symbol in the string. This is because the last numeral is always added to the result.
Loop through the string from the second last character to the first character:

a. If the current symbol is smaller than the next symbol, subtract its value from the result.

b. Otherwise, add its value to the result.

By following this methodology, we can accurately convert any valid Roman numeral string into its integer representation.

Pseudocode

                                            
# Create a mapping from Roman numerals to integers.
roman_to_integer_map = {
'I': 1,
'V': 5,
'X': 10,
'L': 50,
'C': 100,
'D': 500,
'M': 1000
}

# Function to convert Roman numeral to Integer.
function romanToInt(roman_string):

# Initialize result to the value of the last numeral.
result = roman_to_integer_map[roman_string[length of roman_string - 1]]

# Loop through the string from the second last character to the first.
for index from length of roman_string - 2 down to 0:

# If the current numeral is less than the next numeral.
if roman_to_integer_map[roman_string[index]] < roman_to_integer_map[roman_string[index + 1]]:
# Subtract the value of the current numeral from result.
result = result - roman_to_integer_map[roman_string[index]]
else:
# Add the value of the current numeral to result.
result = result + roman_to_integer_map[roman_string[index]]

return result

Let's walk through an example to clarify:

Example: Convert "MCMXCIV"

Initialize
result

with the value of the last numeral "V", so
result = 5

.
Traverse from the second last to the first:

Check "I" (1):

Since 1 (I) < 5 (V), subtract 1 from

result

, now

result = 4

Check "C" (100):

Since 100 (C) < 4 (M), subtract 100, now

result = 104

Check "X" (10):

Since 10 (X) < 100 (C), subtract 10, now

result = 194

Continue until the first element.

By following the above pseudocode and detailed steps, you should be able to convert any valid Roman numeral to its integer counterpart effectively.