Algorithm Roman Numeral Converter - ashish9342/FreeCodeCamp GitHub Wiki
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You will create a program that converts an integer to a Roman Numeral.
Creating two arrays, one with the Roman Numerals and one with the decimal equivalent for the new forms will be very helpful.
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If you add the numbers to the arrays that go before the new letter is introduced, like values for 4, 9, and 40, it will save you plenty of code.
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You can't have more than three consecutive Roman numerals together.
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Solution ahead!
var convertToRoman = function(num) {
var decimalValue = [ 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 ];
var romanNumeral = [ 'M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I' ];
var romanized = '';
for (var index = 0; index < decimalValue.length; index++) {
while (decimalValue[index] <= num) {
romanized += romanNumeral[index];
num -= decimalValue[index];
}
}
return romanized;
}
// test here
convertToRoman(36);
🚀 Run Code
- We start off by creating two arrays with default conversion with matching indices. These are called
decimalValue
andromanNumeral
. We also create an empty string variable,romanized
, which will house the final roman number. - Using a for loop, we loop through the indicies of the
decimalValue
array. We continue to loop until while the value at the currentindex
will fit intonum
. - Next, we add the roman numeral and decrease
num
by the decimal equivalent. - Finally, we return the value of
romanized
.
function convertToRoman(num) {
var romans = ["I", "V", "X", "L", "C", "D", "M"],
ints = [],
romanNumber = [],
numeral = "";
while (num) {
ints.push(num % 10);
num = Math.floor(num/10);
}
for (i=0; i<ints.length; i++){
units(ints[i]);
}
function units(){
numeral = romans[i*2];
switch(ints[i]) {
case 1:
romanNumber.push(numeral);
break;
case 2:
romanNumber.push(numeral.concat(numeral));
break;
case 3:
romanNumber.push(numeral.concat(numeral).concat(numeral));
break;
case 4:
romanNumber.push(numeral.concat(romans[(i*2)+1]));
break;
case 5:
romanNumber.push(romans[(i*2)+1]);
break;
case 6:
romanNumber.push(romans[(i*2)+1].concat(numeral));
break;
case 7:
romanNumber.push(romans[(i*2)+1].concat(numeral).concat(numeral));
break;
case 8:
romanNumber.push(romans[(i*2)+1].concat(numeral).concat(numeral).concat(numeral));
break;
case 9:
romanNumber.push(romans[i*2].concat(romans[(i*2)+2]));
}
}
return romanNumber.reverse().join("").toString();
}
// test here
convertToRoman(97);
🚀 Run Code
- Create an array of Roman Numerals (
romans
). - Use a for loop to create an array of the digits (
ints
) in the number. - Loop through the array of digits (base 10) and as you do, increment the Roman Numeral (base 5) index by 2 (
numeral = romans[i*2]
). - Within the loop, use Switch Case to push the proper Roman Numerals (backwards) onto that array.
- Reverse the Roman Numerals array and turn it into a string.
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