Integer To Roman Conversion Program Solution

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Problem Statement

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol       Value
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

For example, 2 is written as II in Roman numeral, just two one’s added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

• I can be placed before V (5) and X (10) to make 4 and 9. 
• X can be placed before L (50) and C (100) to make 40 and 90. 
• C can be placed before D (500) and M (1000) to make 400 and 900.

Given an integer, convert it to a roman numeral.

Example 1:

Input: num = 3
Output: "III"
Explanation: 3 is represented as 3 ones.

Example 2:

Input: num = 58
Output: "LVIII"
Explanation: L = 50, V = 5, III = 3.

Example 3:

Input: num = 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

Constraints:

• 1 <= num <= 3999

Approach 1: Greedy

• Time: O(1)O(1)
• Space: O(1)O(1)

Integer To Roman Conversion Program Solution In C++

class Solution {
 public:
  string intToRoman(int num) {
    const vector<pair<int, string>> valueSymbols{
        {1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"}, {100, "C"},
        {90, "XC"},  {50, "L"},   {40, "XL"}, {10, "X"},   {9, "IX"},
        {5, "V"},    {4, "IV"},   {1, "I"}};
    string ans;

    for (const auto& [value, symbol] : valueSymbols) {
      if (num == 0)
        break;
      while (num >= value) {
        num -= value;
        ans += symbol;
      }
    }

    return ans;
  }
};

Integer To Roman Conversion Program Solution In JAVA

class Solution {
  public String intToRoman(int num) {
    final int[] values = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
    final String[] symbols = {"M",  "CM", "D",  "CD", "C",  "XC", "L",
                              "XL", "X",  "IX", "V",  "IV", "I"};
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < values.length; ++i) {
      if (num == 0)
        break;
      while (num >= values[i]) {
        num -= values[i];
        sb.append(symbols[i]);
      }
    }

    return sb.toString();
  }
}

Integer To Roman Conversion Program Solution In PYTHON

class Solution:
  def intToRoman(self, num: int) -> str:
    valueSymbols = [(1000, 'M'), (900, 'CM'),
                    (500, 'D'), (400, 'CD'),
                    (100, 'C'), (90, 'XC'),
                    (50, 'L'), (40, 'XL'),
                    (10, 'X'), (9, 'IX'),
                    (5, 'V'), (4, 'IV'),
                    (1, 'I')]
    ans = []

    for value, symbol in valueSymbols:
      if num == 0:
        break
      count, num = divmod(num, value)
      ans.append(symbol * count)

    return ''.join(ans)

Approach 2: Hash Table

• Time: O(1)O(1)
• Space: O(1)O(1)

Integer To Roman Conversion Program Solution In C++ | 2nd Approach

class Solution {
 public:
  string intToRoman(int num) {
    const vector<string> M{"", "M", "MM", "MMM"};
    const vector<string> C{"",  "C",  "CC",  "CCC",  "CD",
                           "D", "DC", "DCC", "DCCC", "CM"};
    const vector<string> X{"",  "X",  "XX",  "XXX",  "XL",
                           "L", "LX", "LXX", "LXXX", "XC"};
    const vector<string> I{"",  "I",  "II",  "III",  "IV",
                           "V", "VI", "VII", "VIII", "IX"};
    return M[num / 1000] + C[num % 1000 / 100] + X[num % 100 / 10] +
           I[num % 10];
  }
};

Integer To Roman Conversion Program Solution In JAVA | 2nd Approach

class Solution {
  public String intToRoman(int num) {
    final String[] M = {"", "M", "MM", "MMM"};
    final String[] C = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
    final String[] X = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
    final String[] I = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
    return M[num / 1000] + C[num % 1000 / 100] + X[num % 100 / 10] + I[num % 10];
  }
}

Integer To Roman Conversion Program Solution In JAVA | 2nd Approach

class Solution:
  def intToRoman(self, num: int) -> str:
    M = ['', 'M', 'MM', 'MMM']
    C = ['', 'C', 'CC', 'CCC', 'CD', 'D', 'DC', 'DCC', 'DCCC', 'CM']
    X = ['', 'X', 'XX', 'XXX', 'XL', 'L', 'LX', 'LXX', 'LXXX', 'XC']
    I = ['', 'I', 'II', 'III', 'IV', 'V', 'VI', 'VII', 'VIII', 'IX']
    return M[num // 1000] + C[num % 1000 // 100] + X[num % 100 // 10] + I[num % 10]

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