Peak Index in a Mountain Array

Author: saurabhchris1

Peak_Index_in_a_Mountain_Array.py

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+# Let's call an array A a mountain if the following properties hold:
+#
+# A.length >= 3
+# There exists some 0 < i < A.length - 1 such that
+# A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1]
+# Given an array that is definitely a mountain, return any i
+# such that A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1].
+
+# Example 1:
+#
+# Input: [0,1,0]
+# Output: 1
+# Example 2:
+#
+# Input: [0,2,1,0]
+# Output: 1
+
+
+class Solution:
+    def peakIndexInMountainArray(self, A):
+
+        l = 0
+        r = len(A) - 1
+
+        while l <= r:
+            m = l + (r - l) // 2
+            if m >= 1 and A[m] > A[m - 1] and A[m] > A[m + 1]:
+                return m
+            elif A[m] > A[m - 1]:
+                l = m + 1
+            else:
+                r = m - 1