[3] Roman to Integer

itpark1018/PalindromeNumber.java

@@ -0,0 +1,19 @@
+package itpark1018;
+
+import java.util.Stack;
+
+public class PalindromeNumber {
+  public boolean isPalindrome(int x) {
+    String xString = Integer.toString(x);
+    Stack<Character> stack = new Stack<>();
+    for (int i = 0; i < xString.length(); i++) {
+      stack.push(xString.charAt(i));
+    }
+
+    StringBuilder stringBuilder = new StringBuilder();
+    while (!stack.isEmpty()) {
+      stringBuilder.append(stack.pop());
+    }
+    return stringBuilder.toString().equals(xString);
+  }
+}

itpark1018/RomanToInteger.java

@@ -0,0 +1,35 @@
+package itpark1018;
+
+import java.util.HashMap;
+
+public class RomanToInteger {
+  public int romanToInt(String s) {
+
+    HashMap<Character, Integer> romanValues = new HashMap<>();
+    romanValues.put('I', 1);
+    romanValues.put('V', 5);
+    romanValues.put('X', 10);
+    romanValues.put('L', 50);
+    romanValues.put('C', 100);
+    romanValues.put('D', 500);
+    romanValues.put('M', 1000);
+
+    int result = 0;
+    int preValue = 0;
+
+    for (int i = s.length() - 1; i >= 0 ; i--) {
+
+      int value = romanValues.get(s.charAt(i));
+
+      if (value < preValue) {
+        result -= value;
+      } else {
+        result += value;
+      }
+
+      preValue = value;
+    }
+
+    return result;
+  }
+}