refactor 69

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_69.java

@@ -2,25 +2,32 @@
 
 /**
  * 69. Sqrt(x)
+ *
  * Implement int sqrt(int x).
  * Compute and return the square root of x.
  */
 
 public class _69 {
-    public int mySqrt(int x) {
-        long left = 0;
-        long right = x / 2 + 1;
-        while (left <= right) {
-            long mid = left + (right - left) / 2;
-            long result = mid * mid;
-            if (result == (long) x) {
-                return (int) mid;
-            } else if (result > x) {
-                right = mid - 1;
-            } else {
-                left = mid + 1;
+    public static class Solution1 {
+        /**A few key points:
+         * 1. all variable use long type, otherwise overflow, just cast to int before returning
+         * 2. left start from 0, not 1
+         * 3. right start from x/2 + 1, not from x*/
+        public int mySqrt(int x) {
+            long left = 0;
+            long right = x / 2 + 1;
+            while (left <= right) {
+                long mid = left + (right - left) / 2;
+                long result = mid * mid;
+                if (result == (long) x) {
+                    return (int) mid;
+                } else if (result > x) {
+                    right = mid - 1;
+                } else {
+                    left = mid + 1;
+                }
             }
+            return (int) right;
         }
-        return (int) right;
     }
 }

src/test/java/com/fishercoder/_69Test.java

@@ -1,39 +1,26 @@
 package com.fishercoder;
 
 import com.fishercoder.solutions._69;
-import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
 import static junit.framework.Assert.assertEquals;
 
-/**
- * Created by fishercoder on 1/25/17.
- */
 public class _69Test {
-    private static _69 test;
-    private static int expected;
-    private static int actual;
-    private static int input;
+  private static _69.Solution1 solution1;
 
-    @BeforeClass
-    public static void setup() {
-        test = new _69();
-    }
+  @BeforeClass
+  public static void setup() {
+    solution1 = new _69.Solution1();
+  }
 
-    @Before
-    public void setupForEachTest() {
-        expected = 0;
-        actual = 0;
-        input = 0;
-    }
+  @Test
+  public void test1() {
+    assertEquals(4, solution1.mySqrt(16));
+  }
 
-    @Test
-    public void test1() {
-        expected = 4;
-        input = 16;
-        actual = test.mySqrt(input);
-        assertEquals(expected, actual);
-
-    }
+  @Test
+  public void test2() {
+    assertEquals(2, solution1.mySqrt(8));
+  }
 }