solves peak index in mountain array

Author: anishLearnsToCode

Diff for: README.md

@@ -229,7 +229,7 @@
 | 840 | [Magic Squares in Grid](https://leetcode.com/problems/magic-squares-in-grid) | |
 | 844 | [Backspace String Compare](https://leetcode.com/problems/backspace-string-compare) | [![Java](assets/java.png)](src/BackspaceStringCompare.java) |
 | 849 | [Maximize Distance to Closest Person](https://leetcode.com/problems/maximize-distance-to-closest-person) | |
-| 852 | [Peak Index in Mountain Array](https://leetcode.com/problems/peak-index-in-a-mountain-array) | |
+| 852 | [Peak Index in Mountain Array](https://leetcode.com/problems/peak-index-in-a-mountain-array) | [![Java](assets/java.png)](src/PeakIndexInMountainArray.java) |
 | 859 | [Buddy Strings](https://leetcode.com/problems/buddy-strings) | |
 | 860 | [Lemonade Change](https://leetcode.com/problems/lemonade-change) | |
 | 867 | [Transpose Matrix](https://leetcode.com/problems/transpose-matrix) | |

Diff for: src/PeakIndexInMountainArray.java

@@ -0,0 +1,8 @@
+public class PeakIndexInMountainArray {
+    public int peakIndexInMountainArray(int[] arr) {
+        for (int index = 1 ; index < arr.length ; index++) {
+            if (arr[index] < arr[index - 1]) return index - 1;
+        }
+        return -1;
+    }
+}