edit 537

src/main/java/com/fishercoder/solutions/_396.java

@@ -52,10 +52,28 @@ private int[] rotate(int[] a) {
         a[a.length-1] = first;
         return a;
     }
+
+    //**credit : https://discuss.leetcode.com/topic/58459/java-o-n-solution-with-explanation
+    public int maxRotateFunction1(int[] A) {
+        int allSum = 0;
+        int len = A.length;
+        int F = 0;
+        for (int i = 0; i < len; i++) {
+            F += i * A[i];
+            allSum += A[i];
+        }
+        int max = F;
+        for (int i = len - 1; i >= 1; i--) {
+            F = F + allSum - len * A[i];
+            max = Math.max(F, max);
+        }
+        return max;
+    }
 
     public static void main(String...strings){
         int[] nums = new int[]{4, 3, 2, 6};
         _396 test = new _396();
         System.out.println(test.maxRotateFunction(nums));
+        System.out.println(test.maxRotateFunction1(nums));
     }
 }

src/main/java/com/fishercoder/solutions/_537.java

@@ -51,5 +51,17 @@ private String multiply(String p, String withI) {
         return String.valueOf(numberPart * Integer.valueOf(p)) + "i";
     }
 
-
+/* Mathematical Solution
+(a + ib) * (x + iy) = ax + by(i^2) + i(bx + ay) = ax - by + i(bx+ay)
+credit : https://leetcode.com/problems/complex-number-multiplication/solution/
+*/
+public String complexNumberMultiply2(String a, String b) {
+    String[] m = a.split("\\+|i");
+    String[] n = b.split("\\+|i");
+    int aFirst = Integer.parseInt(m[0]);
+    int aSecond = Integer.parseInt(m[1]);
+    int bFirst =  Integer.parseInt(n[0]);
+    int bSecond = Integer.parseInt(n[1]);
+    return(aFirst * bFirst - aSecond*bSecond) + "+" + (aFirst * bSecond + aSecond * bFirst) + "i";
+}
 }

src/test/java/com/fishercoder/_606Test.java

@@ -20,7 +20,7 @@ public static void setup(){
     }
 
     @Test
-    public void test1(){
+    public void test1() {
         t = new TreeNode(1);
         t.left = new TreeNode(2);
         t.right = new TreeNode(3);
@@ -30,12 +30,21 @@ public void test1(){
     }
 
     @Test
-    public void test2(){
+    public void test2() {
         t = new TreeNode(1);
         t.left = new TreeNode(2);
         t.right = new TreeNode(3);
         t.left.right = new TreeNode(4);
         System.out.println("Test2");
         assertEquals("1(2()(4))(3)", test.tree2str(t));
     }
+
+    @Test
+    public void test3() {
+        t= new TreeNode(1);
+        t.right = new TreeNode(2);
+        t.right.right = new TreeNode(3);
+        System.out.println("Test3");
+        assertEquals("1()(2()(3))", test.tree2str(t));
+    }
 }