refactor 922

fishercoder1534 · fishercoder1534 · commit 427ad19365e8 · 2021-09-28T10:13:22.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_922.java b/src/main/java/com/fishercoder/solutions/_922.java
@@ -1,24 +1,93 @@
 package com.fishercoder.solutions;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class _922 {
     public static class Solution1 {
-        public int[] sortArrayByParityII(int[] A) {
-            for (int i = 0, j = 1; i < A.length - 1 && j < A.length; ) {
-                if (A[i] % 2 != 0 && A[j] % 2 == 0) {
-                    int tmp = A[i];
-                    A[i] = A[j];
-                    A[j] = tmp;
+        /**
+         * Space: O(n)
+         * Time: O(n)
+         */
+        public int[] sortArrayByParityII(int[] nums) {
+            List<Integer> odds = new ArrayList<>();
+            List<Integer> evens = new ArrayList<>();
+            for (int i = 0; i < nums.length; i++) {
+                if (nums[i] % 2 == 0) {
+                    evens.add(nums[i]);
+                } else {
+                    odds.add(nums[i]);
+                }
+            }
+            int oddIndex = 0;
+            int evenIndex = 0;
+            for (int i = 0; i < nums.length; i++) {
+                if (i % 2 == 0) {
+                    nums[i] = evens.get(evenIndex++);
+                } else {
+                    nums[i] = odds.get(oddIndex++);
+                }
+            }
+            return nums;
+        }
+    }
+
+    public static class Solution2 {
+        /**
+         * Space: O(1)
+         * Time: O(n^2)
+         */
+        public int[] sortArrayByParityII(int[] nums) {
+            for (int i = 0; i < nums.length; i++) {
+                if (i % 2 == 0 && nums[i] % 2 != 0) {
+                    for (int j = i + 1; j < nums.length; j++) {
+                        if (j % 2 != 0 && nums[j] % 2 == 0) {
+                            int tmp = nums[j];
+                            nums[j] = nums[i];
+                            nums[i] = tmp;
+                            break;
+                        }
+                    }
+                } else if (i % 2 != 0 && nums[i] % 2 == 0) {
+                    for (int j = i + 1; j < nums.length; j++) {
+                        if (j % 2 == 0 && nums[j] % 2 != 0) {
+                            int tmp = nums[j];
+                            nums[j] = nums[i];
+                            nums[i] = tmp;
+                            break;
+                        }
+                    }
+                }
+            }
+            return nums;
+        }
+    }
+
+    public static class Solution3 {
+        /**
+         * This is the most efficient solution: one implicit condition is that:
+         * we start with index zero for i, so we look for nums[i] that is not an even number to be swapped with;
+         * we start with index one for j, so we look for nums[j] that is not an odd number to be swapped with.
+         * Time: O(n)
+         * Space: O(1)
+         */
+        public int[] sortArrayByParityII(int[] nums) {
+            for (int i = 0, j = 1; i < nums.length - 1 && j < nums.length; ) {
+                if (nums[i] % 2 != 0 && nums[j] % 2 == 0) {
+                    int tmp = nums[i];
+                    nums[i] = nums[j];
+                    nums[j] = tmp;
                     i += 2;
                     j += 2;
                 }
-                while (i < A.length - 1 && A[i] % 2 == 0) {
+                while (i < nums.length - 1 && nums[i] % 2 == 0) {
                     i += 2;
                 }
-                while (j < A.length && A[j] % 2 != 0) {
+                while (j < nums.length && nums[j] % 2 != 0) {
                     j += 2;
                 }
             }
-            return A;
+            return nums;
         }
     }
 }
diff --git a/src/test/java/com/fishercoder/_922Test.java b/src/test/java/com/fishercoder/_922Test.java
@@ -7,25 +7,70 @@
 
 public class _922Test {
     private static _922.Solution1 solution1;
-    private static int[] A;
+    private static _922.Solution2 solution2;
+    private static _922.Solution3 solution3;
+    private static int[] nums;
     private static int[] result;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _922.Solution1();
+        solution2 = new _922.Solution2();
+        solution3 = new _922.Solution3();
     }
 
     @Test
     public void test1() {
-        A = new int[]{4, 2, 5, 7};
-        result = solution1.sortArrayByParityII(A);
+        nums = new int[]{4, 2, 5, 7};
+        result = solution1.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution2.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution3.sortArrayByParityII(nums);
         CommonUtils.printArray(result);
     }
 
     @Test
     public void test2() {
-        A = new int[]{3, 1, 4, 2};
-        result = solution1.sortArrayByParityII(A);
+        nums = new int[]{3, 1, 4, 2};
+        result = solution1.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution2.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution3.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+    }
+
+    @Test
+    public void test3() {
+        nums = new int[]{648, 831, 560, 986, 192, 424, 997, 829, 897, 843};
+        result = solution1.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution2.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution3.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+    }
+
+    @Test
+    public void test4() {
+        nums = new int[]{3, 4};
+        result = solution1.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution2.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution3.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+    }
+
+    @Test
+    public void test5() {
+        nums = new int[]{2, 3, 1, 1, 4, 0, 0, 4, 3, 3};
+        result = solution1.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution2.sortArrayByParityII(nums);
+        CommonUtils.printArray(result);
+        result = solution3.sortArrayByParityII(nums);
         CommonUtils.printArray(result);
     }
 }
