[N-0] refactor 7

fishercoder1534 · fishercoder1534 · commit 2e63b322c856 · 2017-12-02T08:13:25.000-08:00
diff --git a/src/main/java/com/fishercoder/solutions/_7.java b/src/main/java/com/fishercoder/solutions/_7.java
@@ -1,82 +1,28 @@
 package com.fishercoder.solutions;
-/**7. Reverse Integer
-Reverse digits of an integer.
 
-Example1: x = 123, return 321
-Example2: x = -123, return -321*/
-public class _7 {
-    public int reverse_short_version(int x) {
-        long rev = 0;
-        while (x != 0) {
-            rev = rev * 10 + x % 10;
-            x /= 10;
-            if (rev > Integer.MAX_VALUE || rev < Integer.MIN_VALUE) {
-                return 0;
-            }
-        }
-        return (int) rev;
-    }
+/**
+ * 7. Reverse Integer
+ *
+ * Reverse digits of an integer.
 
-    public int reverse(int x) {
-        if (x == 0) {
-            return 0;
-        }
-        //save the first bit if it's a negative sign
-        StringBuilder sb = new StringBuilder();
-        sb.append(x);
-        boolean negative = sb.toString().charAt(0) == '-' ? true : false;
-        //use modulor and division and use long as the result type to avoid overflow
-        long longX = (long) x;
-        if (negative) {
-            //get rid of the first '-' bit
-            String withoutNegativeSign = sb.substring(1).toString();
-            longX = Long.parseLong(withoutNegativeSign);
-        }
-        sb.setLength(0);
-        long result = 0;
-        if (negative) {
-            sb.append('-');
-        }
-        while (longX != 0) {
-            sb.append(longX % 10);
-            longX /= 10;
-        }
-        result = Long.parseLong(sb.toString());
-        System.out.println(result);//it's right here, but after converting it into an int, it overflowed to become a wrong number, how to handle this?
-        //it turns out depending on the question requirement, on this OJ, it's expecting 0, if it's beyond the range of (Integer.MIN_VALUE, Integer.MAX_VALUE)
-        return (result > Integer.MAX_VALUE || result < Integer.MIN_VALUE) ? 0 : (int) result;
-    }
+ Example1: x = 123, return 321
 
-    public static void main(String... strings) {
-        _7 test = new _7();
-        //when the input is 1534236469, it's expecting 0 as the correct answer, this is due to its reversed number is greater than Integer.MAX_VALUE, thus return 0
-        System.out.println(1534236469 > Integer.MAX_VALUE);
-        System.out.println("1534236469\n" + Integer.MAX_VALUE);
-//        System.out.println(test.reverse(-2147483648));
-    }
+ Example2: x = -123, return -321
 
-    // this is not going to work when the input number's reverse version is greater than
-    // Integer.MAX_VALUE, it'll throw NumberFormatException as Java cannot handle it, overflowed.
-    public int reverse_overflowed(int x) {
-        //save the first bit if it's a negative sign
-        StringBuilder sb = new StringBuilder();
-        sb.append(x);
-        boolean negative = sb.toString().charAt(0) == '-' ? true : false;
-        char[] bits = sb.toString().toCharArray();
-        sb.setLength(0);
-        if (negative) {
-            sb.append('-');
-            //until i > 0
-            for (int i = bits.length - 1; i > 0; i--) {
-                sb.append(bits[i]);
-            }
-        } else {
-            //until i >= 0
-            for (int i = bits.length - 1; i >= 0; i--) {
-                sb.append(bits[i]);
+ */
+public class _7 {
+
+    public static class Solution1 {
+        public int reverse(int x) {
+            long rev = 0;
+            while (x != 0) {
+                rev = rev * 10 + x % 10;
+                x /= 10;
+                if (rev > Integer.MAX_VALUE || rev < Integer.MIN_VALUE) {
+                    return 0;
+                }
             }
+            return (int) rev;
         }
-        return Integer.parseInt(sb.toString());
     }
-
 }
diff --git a/src/test/java/com/fishercoder/_7Test.java b/src/test/java/com/fishercoder/_7Test.java
@@ -0,0 +1,23 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._7;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _7Test {
+    private static _7.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _7.Solution1();
+    }
+
+    @Test
+    public void test1() {
+//        its reversed number is greater than Integer.MAX_VALUE, thus return 0
+        assertEquals(0, solution1.reverse(1534236469));
+    }
+
+}
