update 162

Author: fishercoder1534

Diff for: src/main/java/com/fishercoder/solutions/_162.java

@@ -4,29 +4,31 @@ public class _162 {
 
     public static class Solution1 {
         /**
-         * credit: https://discuss.leetcode.com/topic/29329/java-solution-and-explanation-using-invariants
-         * <p>
-         * Basically, we need to keep this invariant:
-         * nums[left] > nums[left-1], then we could return left as the result
-         * or nums[right] > nums[right+1], then we could return right as the result
-         * <p>
+         * credit: https://leetcode.com/problems/find-peak-element/solutions/1290642/intuition-behind-conditions-complete-explanation-diagram-binary-search/
          * Time: O(logn)
+         * <p>
+         * draw three cases with three examples, it's pretty self-explanatory
          */
         public int findPeakElement(int[] nums) {
-            if (nums == null || nums.length == 0) {
+            if (nums == null || nums.length <= 1 || nums[0] > nums[1]) {
                 return 0;
             }
-            int left = 0;
-            int right = nums.length - 1;
-            while (left + 1 < right) {
+            if (nums[nums.length - 1] > nums[nums.length - 2]) {
+                return nums.length - 1;
+            }
+            int left = 1;
+            int right = nums.length - 2;
+            while (left <= right) {
                 int mid = left + (right - left) / 2;
-                if (nums[mid] < nums[mid + 1]) {
-                    left = mid;
-                } else {
-                    right = mid;
+                if (nums[mid] > nums[mid - 1] && nums[mid] > nums[mid + 1]) {
+                    return mid;
+                } else if (nums[mid] < nums[mid - 1]) {
+                    right = mid - 1;
+                } else if (nums[mid] < nums[mid + 1]) {
+                    left = mid + 1;
                 }
             }
-            return (left == nums.length - 1 || nums[left] > nums[left + 1]) ? left : right;
+            return -1;
         }
     }
 

Diff for: src/test/java/com/fishercoder/_162Test.java

@@ -1,18 +1,18 @@
 package com.fishercoder;
 
 import com.fishercoder.solutions._162;
-import org.junit.BeforeClass;
-import org.junit.Test;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
 
-import static org.junit.Assert.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class _162Test {
     private static _162.Solution1 solution1;
     private static _162.Solution2 solution2;
     private static int[] nums;
 
-    @BeforeClass
-    public static void setup() {
+    @BeforeEach
+    public void setup() {
         solution1 = new _162.Solution1();
         solution2 = new _162.Solution2();
     }