integer_to_roman.md

🔥 Integer to Roman 🔥 || 5 Solutions || Simple Fast and Easy || with Explanation

Solution - 1

class Solution {
  String intToRoman(int num) {
    //first we create a table of roman word and their values..
    List<String> romanWord = [
      "I",
      "IV",
      "V",
      "IX",
      "X",
      "XL",
      "L",
      "XC",
      "C",
      "CD",
      "D",
      "CM",
      "M"
    ];
    List<int> value = [1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000];
    //initialize and set the index i...
    int i = romanWord.length - 1;
    //create the solution which will be in string format...
    String sol = "";
    //a loop will be made to begin the procedure...
    while (num > 0) {
      //this loop is working until the the value of integer is less or equal to num...
      while (value[i] <= num) {
        //Append the roman numeral into an solution string...
        sol += romanWord[i];
        //subtract the integral value from the given integer...
        //Subtract the current number until the given integer is greater than the current number.
        num -= value[i];
      }
      i--;
    }
    //Once we are done with all the roman numerals, we return the solution.
    return sol;
  }
}

Solution - 2

class Solution {
  String intToRoman(int num) {
    List<int> number = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
    List<String> roman = [
      "M",
      "CM",
      "D",
      "CD",
      "C",
      "XC",
      "L",
      "XL",
      "X",
      "IX",
      "V",
      "IV",
      "I"
    ];

    String res = "";

    for (int i = 0; i <= number.length - 1; i++) {
      if (num / number[i] >= 1) {
        res += roman[i] * (num ~/ number[i]);
        num = num - (num ~/ number[i]) * number[i];
      }
      if (num == 0) break;
    }
    return res;
  }
}

Solution - 3

class C {
  String intToRoman(int num) {
    String romanNumeral = "";
    while (num >= 1000) {
      romanNumeral += "M";
      num -= 1000;
    }
    while (num >= 900) {
      romanNumeral += "CM";
      num -= 900;
    }
    while (num >= 500) {
      romanNumeral += "D";
      num -= 500;
    }
    while (num >= 400) {
      romanNumeral += "CD";
      num -= 400;
    }
    while (num >= 100) {
      romanNumeral += "C";
      num -= 100;
    }
    while (num >= 90) {
      romanNumeral += "XC";
      num -= 90;
    }
    while (num >= 50) {
      romanNumeral += "L";
      num -= 50;
    }
    while (num >= 40) {
      romanNumeral += "XL";
      num -= 40;
    }
    while (num >= 10) {
      romanNumeral += "X";
      num -= 10;
    }
    while (num >= 9) {
      romanNumeral += "IX";
      num -= 9;
    }
    while (num >= 5) {
      romanNumeral += "V";
      num -= 5;
    }
    while (num >= 4) {
      romanNumeral += "IV";
      num -= 4;
    }
    while (num >= 1) {
      romanNumeral += "I";
      num -= 1;
    }

    return romanNumeral;
  }
}

Solution - 4

class Solution {
  String intToRoman(int num) {
    final StringBuffer sb = StringBuffer();
    final List<String> thousands = ["", "M", "MM", "MMM"];
    final List<String> hundreds = [
      "",
      "C",
      "CC",
      "CCC",
      "CD",
      "D",
      "DC",
      "DCC",
      "DCCC",
      "CM"
    ];
    final List<String> tens = [
      "",
      "X",
      "XX",
      "XXX",
      "XL",
      "L",
      "LX",
      "LXX",
      "LXXX",
      "XC"
    ];
    final List<String> ones = [
      "",
      "I",
      "II",
      "III",
      "IV",
      "V",
      "VI",
      "VII",
      "VIII",
      "IX"
    ];

    sb.write(thousands[num ~/ 1000]);
    sb.write(hundreds[(num % 1000) ~/ 100]);
    sb.write(tens[(num % 100) ~/ 10]);
    sb.write(ones[num % 10]);

    return sb.toString();
  }
}

Solution - 5

import 'dart:collection';
class Solution {
  HashMap<int, String> up = HashMap();
  String intToRoman(int num) {
    up[5] = "V";
    up[10] = "X";
    up[50] = "L";
    up[100] = "C";
    up[500] = "D";
    up[1000] = "M";
    return comp(num);
  }

  String comp(int num) {
    if (num == 0) return "";
    if (num == 1) {
      return "I";
    }
    if (num == 2) return "II";
    if (num == 3) {
      return "III";
    }
    if (num == 4) {
      return "IV";
    }
    if (num == 9) {
      return "IX";
    }
    if (num >= 40 && num < 50) {
      return "XL" + comp(num - 40);
    }
    if (num >= 90 && num < 100) {
      return "XC" + comp(num - 90);
    }
    if (num >= 400 && num < 500) {
      return "CD" + comp(num - 400);
    }
    if (num >= 900 && num < 1000) {
      return "CM" + comp(num - 900);
    }

    List<int> arr = [5, 10, 50, 100, 500, 1000];
    int i = 0;
    for (; i <= 5; i++) {
      if (arr[i] > num) break;
    }

    int val = arr[i - 1];
    return up[val]! + comp(num - val);
  }
}