add

5.leetcode/src/com/fanxb/common/Q12.java

@@ -0,0 +1,68 @@
+package com.fanxb.common;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Created with IntelliJ IDEA
+ *
+ * @author fanxb
+ * Date: 2020/6/10 10:49
+ */
+public class Q12 {
+
+    public String intToRoman(int num) {
+        StringBuilder stringBuilder = new StringBuilder();
+        while (num > 0) {
+            if (num >= 1000) {
+                stringBuilder.append("M");
+                num -= 1000;
+            } else if (num >= 900) {
+                stringBuilder.append("CM");
+                num -= 900;
+            } else if (num >= 500) {
+                stringBuilder.append("D");
+                num -= 500;
+            } else if (num >= 400) {
+                stringBuilder.append("CD");
+                num -= 400;
+            } else if (num >= 100) {
+                stringBuilder.append("C");
+                num -= 100;
+            } else if (num >= 90) {
+                stringBuilder.append("XC");
+                num -= 90;
+            } else if (num >= 50) {
+                stringBuilder.append("L");
+                num -= 50;
+            } else if (num >= 40) {
+                stringBuilder.append("XL");
+                num -= 40;
+            } else if (num >= 10) {
+                stringBuilder.append("X");
+                num -= 10;
+            } else if (num == 9) {
+                stringBuilder.append("IX");
+                num -= 9;
+            } else if (num >= 5) {
+                stringBuilder.append("V");
+                num -= 5;
+            } else if (num == 4) {
+                stringBuilder.append("IV");
+                num -= 4;
+            } else {
+                stringBuilder.append("I");
+                num -= 1;
+            }
+        }
+        return stringBuilder.toString();
+    }
+
+    public static void main(String[] args) {
+        Q12 instance = new Q12();
+        System.out.println(instance.intToRoman(3));
+        System.out.println(instance.intToRoman(9));
+        System.out.println(instance.intToRoman(58));
+        System.out.println(instance.intToRoman(1994));
+    }
+}

5.leetcode/src/com/fanxb/common/Q13.java

@@ -0,0 +1,45 @@
+package com.fanxb.common;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Created with IntelliJ IDEA
+ *
+ * @author fanxb
+ * Date: 2020/6/10 10:49
+ */
+public class Q13 {
+    private static Map<Character, Integer> map = new HashMap<>(7);
+
+    static {
+        map.put('I', 1);
+        map.put('V', 5);
+        map.put('X', 10);
+        map.put('L', 50);
+        map.put('C', 100);
+        map.put('D', 500);
+        map.put('M', 1000);
+    }
+
+    public int romanToInt(String s) {
+        int res = 0;
+        char[] chars = s.toCharArray();
+        int length = chars.length;
+        for (int i = 0; i < length; i++) {
+            int cur = map.get(chars[i]), next = i == length - 1 ? 0 : map.get(chars[i + 1]);
+            if (cur < next) {
+                res += next - cur;
+                i++;
+            } else {
+                res += cur;
+            }
+        }
+        return res;
+    }
+
+    public static void main(String[] args) {
+        Q13 instance = new Q13();
+        System.out.println(instance.romanToInt("MCMXCIVI"));
+    }
+}