Integer to Roman
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Problem Statement Solution 1: Greedy Approach Solution 2: Using a Map Solution 3: Recursive Approach Solution 4: Using String Concatenation Solution 5: Array of Objects Solution 6: Using Recursive Helper Function Solution 7: Using a While Loop with Index Solution 8: Map with Array Reduce Solution 9: Using Array Reduce with Object Solution 10: Using Switch Case for Values More Problems Solutions
Problem Statement
Imagine you’re living in ancient Rome, where numbers are represented with a set of unique symbols. Roman numerals use seven symbols to signify values:
I stands for 1
V stands for 5
X stands for 10
L stands for 50
C stands for 100
D stands for 500
M stands for 1000
To convert a modern-day integer into this ancient numeral system, follow these rules:
Subtracting Values: Some numbers are written using subtraction to avoid four repetitions of a symbol. For example:
4 is written as IV (5 minus 1)
9 is written as IX (10 minus 1)
Similarly, 40 is XL (50 minus 10), 90 is XC (100 minus 10), 400 is CD (500 minus 100), and 900 is CM (1000 minus 100).
Repetition Rules: You can repeat certain symbols up to three times:
Symbols I, X, C, and M can be repeated (e.g., 3 is III, 30 is XXX).
Symbols V, L, and D cannot be repeated. Instead, use the subtractive forms if needed (e.g., 4 is IV, not IIII).
Build from Largest to Smallest: Start with the largest value and work your way down. For example, to convert 3749:
Start with the largest numeral (1000), then move to the next largest (500), and continue until you represent the entire number.
Example 1
Input: n = 3749
Output: "MMMDCCXLIX"
Example 2
Input: n = 58
Output: "LVIII"
Solution 1: Greedy Approach
function intToRomanGreedy(num) {
const values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
const symbols = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];
let result = "";
for (let i = 0; i < values.length; i++) {
while (num >= values[i]) {
result += symbols[i];
num -= values[i];
}
}
return result;
}
const n1 = 3749;
intToRomanGreedy(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanGreedy(n2); //output: LVIII
Solution 2: Using a Map
function intToRomanMap(num) {
const map = new Map([
[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"]
]);
let result = "";
for (const [value, symbol] of map) {
while (num >= value) {
result += symbol;
num -= value;
}
}
return result;
}
const n1 = 3749;
intToRomanMap(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanMap(n2); //output: LVIII
Solution 3: Recursive Approach
function intToRomanRecursive(num) {
const valueSymbolPairs = [
[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"]
];
function convert(n) {
if (n === 0) return "";
for (const [value, symbol] of valueSymbolPairs) {
if (n >= value) {
return symbol + convert(n - value);
}
}
return "";
}
return convert(num);
}
const n1 = 3749;
intToRomanRecursive(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanRecursive(n2); //output: LVIII
Solution 4: Using String Concatenation
function intToRomanStringConcat(num) {
const values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
const symbols = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];
let result = "";
values.forEach((value, index) => {
while (num >= value) {
result += symbols[index];
num -= value;
}
});
return result;
}
const n1 = 3749;
intToRomanStringConcat(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanStringConcat(n2); //output: LVIII
Solution 5: Array of Objects
function intToRomanArrayOfObjects(num) {
const arr = [
{ value: 1000, symbol: "M" }, { value: 900, symbol: "CM" },
{ value: 500, symbol: "D" }, { value: 400, symbol: "CD" },
{ value: 100, symbol: "C" }, { value: 90, symbol: "XC" },
{ value: 50, symbol: "L" }, { value: 40, symbol: "XL" },
{ value: 10, symbol: "X" }, { value: 9, symbol: "IX" },
{ value: 5, symbol: "V" }, { value: 4, symbol: "IV" },
{ value: 1, symbol: "I" }
];
let result = "";
arr.forEach(({ value, symbol }) => {
while (num >= value) {
result += symbol;
num -= value;
}
});
return result;
}
const n1 = 3749;
intToRomanArrayOfObjects(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanArrayOfObjects(n2); //output: LVIII
Solution 6: Using Recursive Helper Function
function intToRoman(num) {
const values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
const symbols = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];
return intToRomanHelper(num, values, symbols);
}
function intToRomanHelper(num, values, symbols) {
if (num === 0) return "";
for (let i = 0; i < values.length; i++) {
if (num >= values[i]) {
return symbols[i] + intToRomanHelper(num - values[i], values, symbols);
}
}
return ""; // Default return if no conditions are met
}
const n1 = 3749;
intToRoman(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRoman(n2); //output: LVIII
Solution 7: Using a While Loop with Index
function intToRomanWhileLoop(num) {
const values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
const symbols = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];
let result = "";
let i = 0;
while (num > 0) {
while (num >= values[i]) {
result += symbols[i];
num -= values[i];
}
i++;
}
return result;
}
const n1 = 3749;
intToRomanWhileLoop(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanWhileLoop(n2); //output: LVIII
Solution 8: Map with Array Reduce
function intToRomanReduce(num) {
// Define the Roman numeral values and their corresponding symbols
const romanMap = new Map([
[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"]
]);
// Use array reduce to build the Roman numeral string
return Array.from(romanMap.entries()).reduce((acc, [value, symbol]) => {
while (num >= value) {
acc += symbol;
num -= value;
}
return acc;
}, "");
}
const n1 = 3749;
intToRomanReduce(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanReduce(n2); //output: LVIII
Solution 9: Using Array Reduce with Object
function intToRomanObjectReduce(num) {
// Define the Roman numeral values and their corresponding symbols
const romanNumerals = [
{ value: 1000, symbol: "M" },
{ value: 900, symbol: "CM" },
{ value: 500, symbol: "D" },
{ value: 400, symbol: "CD" },
{ value: 100, symbol: "C" },
{ value: 90, symbol: "XC" },
{ value: 50, symbol: "L" },
{ value: 40, symbol: "XL" },
{ value: 10, symbol: "X" },
{ value: 9, symbol: "IX" },
{ value: 5, symbol: "V" },
{ value: 4, symbol: "IV" },
{ value: 1, symbol: "I" }
];
// Use array reduce to build the Roman numeral string
return romanNumerals.reduce((acc, { value, symbol }) => {
while (num >= value) {
acc += symbol;
num -= value;
}
return acc;
}, "");
}
const n1 = 3749;
intToRomanObjectReduce(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanObjectReduce(n2); //output: LVIII
Solution 10: Using Switch Case for Values
function intToRomanSwitch(num) {
const 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"]
];
let result = "";
for (const [value, symbol] of valueSymbols) {
while (num >= value) {
result += symbol;
num -= value;
}
}
return result;
}
const n1 = 3749;
intToRomanSwitch(n1); //output: MMMDCCXLIX
const n2 = 58;
intToRomanSwitch(n2); //output: LVIII