LeetCode 12: Integer to Roman Solution

Master LeetCode problem 12 (Integer to Roman), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

12. Integer to Roman

Medium

Hash Table Math String

Problem Explanation

Explanation

To solve this problem, we can iterate over the given integer while reducing it based on the highest Roman numeral value possible at each step. We can create a mapping of Roman numeral symbols to their decimal values and use this mapping to construct the Roman numeral representation of the input integer.

Create a mapping of Roman numeral symbols to their decimal values.
Iterate over the mapping in descending order of decimal values.
At each step, check if the current decimal value can be subtracted from the input integer.
If yes, append the corresponding Roman numeral symbol to the result and subtract its decimal value from the input.
Repeat until the input integer becomes 0.

Time Complexity

The time complexity of this approach is O(1) since the maximum input constraint is 3999, which requires a constant number of operations.

Space Complexity

The space complexity is O(1) as we are using a fixed amount of space for the mapping and the result string.

Solution Code

class Solution {
    public String intToRoman(int num) {
        int[] values = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
        String[] symbols = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
        
        StringBuilder roman = new StringBuilder();
        
        for (int i = 0; i < values.length; i++) {
            while (num >= values[i]) {
                roman.append(symbols[i]);
                num -= values[i];
            }
        }
        
        return roman.toString();
    }
}

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