Roman to Integer

Short summary

Roman numeral conversion follows a subtraction rule: when a smaller numeral precedes a larger one, subtract it; otherwise add. A single left-to-right traversal solves this in O(n) time and O(1) space. Example: MCMIV = 1000 - 100 + 1000 - 1 + 5 = 1904.

• •Compare each digit to the next one: smaller before larger means subtract
• •One-pass algorithm with HashMap lookup
• •O(n) time, O(1) space — efficient for interview coding

Generated with AI, which can make mistakes.