Integer to Roman

Represent Roman values in descending order, including subtractive forms before their components: 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. Repeatedly append the largest symbol whose value does not exceed the remaining integer and subtract that value. Including 900, 400, 90, 40, 9, and 4 prevents invalid additive outputs such as IIII or DCCCC. The greedy choice is valid for the standard canonical Roman numeral system because the table already captures each exceptional representation and larger denominations should be consumed first. Clarify the accepted range, usually 1 through 3999, because there is no universal standard for zero or larger overline notation. Test 4, 9, 58, 1994, exact symbol boundaries, and repeated thousands. The table has constant size, so time is O(number of output symbols) and extra space beyond output is O(1).