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authorJack Sangdahl <[email protected]>2024-10-29 19:53:49 -0600
committerJack Sangdahl <[email protected]>2024-10-29 19:53:49 -0600
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parentbf0ef281bee5004aee7ac459d42d7bab526c6d8a (diff)
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1671. minimum number of removals to make mountain array
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+# 1671. Minimum Number of Removals to Make Mountain Array
+from bisect import bisect_left
+
+"""
+you may recall that an array 'arr' is a mountain array if and only if
+'arr.length >= 3', there exists soome index 'i' with '0 < i < arr.length - 1'
+such that 'arr[0] < arr[1] <... < arr[i - 1]' and 'arr[i] > arr[i + 1] > ...
+> arr[length - 1]'. given an integer array 'nums', return the minimum number
+of elements to remove to make 'nums' a mountain array
+"""
+
+
+class Solution(object):
+ def minimumMountainRemovals(self, nums):
+ """
+ :type nums: List[int]
+ :rtype: int
+ """
+
+ def lis(nums):
+ dp = [10**10] * (len(nums) + 1)
+ lens = [0] * len(nums)
+ for i, j in enumerate(nums):
+ lens[i] = bisect_left(dp, j) + 1
+ dp[lens[i] - 1] = j
+ return lens
+
+ l1, l2 = lis(nums), lis(nums[::-1])[::-1]
+ ans, n = 0, len(nums)
+ for i in range(n):
+ if l1[i] >= 2 and l2[i] >= 2:
+ ans = max(ans, l1[i] + l2[i] - 1)
+ return n - ans
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(obj.minimumMountainRemovals(nums=[1, 3, 1]))
+ print(obj.minimumMountainRemovals(nums=[2, 1, 1, 5, 6, 2, 3, 1]))