solution(python3): 1095. Find in Mountain Array

1095. Find in Mountain Array

Hard/1095. Find in Mountain Array/READEME.md

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+(This problem is an interactive problem.)
+
+You may recall that an array arr is a mountain array if and only if:
+
+arr.length >= 3
+There exists some i with 0 < i < arr.length - 1 such that:
+arr[0] < arr[1] < ... < arr[i - 1] < arr[i]
+arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
+Given a mountain array mountainArr, return the minimum index such that mountainArr.get(index) == target. If such an index does not exist, return -1.
+
+You cannot access the mountain array directly. You may only access the array using a MountainArray interface:
+
+MountainArray.get(k) returns the element of the array at index k (0-indexed).
+MountainArray.length() returns the length of the array.
+Submissions making more than 100 calls to MountainArray.get will be judged Wrong Answer. Also, any solutions that attempt to circumvent the judge will result in disqualification.
+
+
+
+Example 1:
+
+Input: array = [1,2,3,4,5,3,1], target = 3
+Output: 2
+Explanation: 3 exists in the array, at index=2 and index=5. Return the minimum index, which is 2.
+Example 2:
+
+Input: array = [0,1,2,4,2,1], target = 3
+Output: -1
+Explanation: 3 does not exist in the array, so we return -1.

Hard/1095. Find in Mountain Array/solution.py

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+# """
+# This is MountainArray's API interface.
+# You should not implement it, or speculate about its implementation
+# """
+#class MountainArray(object):
+#    def get(self, index):
+#        """
+#        :type index: int
+#        :rtype int
+#        """
+#
+#    def length(self):
+#        """
+#        :rtype int
+#        """
+
+class Solution(object):
+    def findInMountainArray(self, target, mountain_arr):
+        def find_peak(mountain_arr):
+            left, right = 0, mountain_arr.length() - 1
+            while left < right:
+                mid = left + (right - left) // 2
+                if mountain_arr.get(mid) < mountain_arr.get(mid + 1):
+                    left = mid + 1
+                else:
+                    right = mid
+            return left
+
+        def binary_search(left, right, is_increasing):
+            while left <= right:
+                mid = left + (right - left) // 2
+                mid_val = mountain_arr.get(mid)
+                if mid_val == target:
+                    return mid
+                if mid_val < target:
+                    if is_increasing:
+                        left = mid + 1
+                    else:
+                        right = mid - 1
+                else:
+                    if is_increasing:
+                        right = mid - 1
+                    else:
+                        left = mid + 1
+            return -1
+
+        peak_index = find_peak(mountain_arr)
+        result = binary_search(0, peak_index, True)
+        if result == -1:
+            result = binary_search(peak_index + 1, mountain_arr.length() - 1, False)
+        return result