Create IntToRoman.java

Author: huangsam

java/IntToRoman.java

@@ -0,0 +1,36 @@
+// https://leetcode.com/problems/integer-to-roman/
+
+public class IntToRoman {
+    /**
+     * Convert integer to Roman numeral. We start by holding
+     * all the Roman mappings in an array, along with edge cases
+     * like 900, 400, 90, 40, 9, 4. We then iterate through the
+     * array and keep subtracting the value from the number until
+     * we reach 0.
+     */
+    public String intToRoman(int num) {
+        Roman[] romans = new Roman[] { // Includes 900, 400, 90, 40, 9, 4
+            new Roman(1000, "M"), new Roman(900, "CM"),
+            new Roman(500, "D"), new Roman(400, "CD"),
+            new Roman(100, "C"), new Roman(90, "XC"),
+            new Roman(50, "L"), new Roman(40, "XL"),
+            new Roman(10, "X"), new Roman(9, "IX"),
+            new Roman(5, "V"), new Roman(4, "IV"),
+            new Roman(1, "I")
+        };
+        int pointer = 0;
+        StringBuilder builder = new StringBuilder();
+        while (num > 0) {
+            Roman roman = romans[pointer];
+            while (num >= roman.value()) {
+                num -= roman.value();
+                builder.append(roman.code());
+            }
+            pointer++;
+        }
+        return builder.toString();
+    }
+
+    private record Roman(int value, String code) {
+    }
+}