Merge pull request #1122 from vandit98/first_repeat_python

adding longest_peak in python

Author: akgmage

Arrays/longest_peak.py

@@ -0,0 +1,47 @@
+"""
+Write a function that takes in an array of integers and returns the length of the longest peak
+in the array.A peak is defined as adjacent integers in the array that are strictly increasing
+until they reach a tip (the highest value in the peak), at which point they become strictly 
+decreasing. At least three integers are required to form a peak.
+"""
+
+
+
+#approach
+"""
+1. iterate through the array from index 1 to len(arr) - 1
+2. check if the current element is a peak
+3. if it is a peak, then find the length of the peak
+4. go to the uphill start
+5. go to the downhill end
+6. update the ans
+"""
+# Time Complexity: O(n)
+# Space Complexity: O(1)
+
+
+
+arr=[1, 2, 3, 3, 4, 0, 10, 6, 5, -1, -3, 2, 3]
+
+
+def longestPeak(arr: list) -> int:
+        ans = 0
+        # iterate through the array from index 1 to len(arr) - 1
+        for indx in range(1, len(arr) - 1):
+            # check if the current element is a peak
+            if arr[indx - 1] < arr[indx] > arr[indx + 1]:
+                # if it is a peak, then find the length of the peak
+                uphill_start = downhill_ends = indx
+                # go to the uphill start
+                while uphill_start > 0 and arr[uphill_start] > arr[uphill_start - 1]:
+                    uphill_start -= 1
+                    # go to the downhill end
+                while downhill_ends + 1 < len(arr) and arr[downhill_ends] > arr[downhill_ends + 1]:
+                    downhill_ends += 1
+                    # update the ans 
+                ans = max(ans, (downhill_ends - uphill_start + 1))
+        return ans
+
+
+print(longestPeak(arr))
+# output: 6