Find Maximum Non-decreasing Array Length — LeetCode 2945 Python Solution

The problem

You are given a 0-indexed integer array nums. You can perform any number of operations, where each operation involves selecting a subarray of the array and replacing it with the sum of its elements.

Example

Input

nums = [5,2,2]

Output

1

Explanation

This array with length 3 is not non-decreasing.

Python solution

class Solution:
    def findMaximumLength(self, nums: List[int]) -> int:
        n = len(nums)
        s = list(accumulate(nums, initial=0))
        f = [0] * (n + 1)
        pre = [0] * (n + 2)
        for i in range(1, n + 1):
            pre[i] = max(pre[i], pre[i - 1])
            f[i] = f[pre[i]] + 1
            j = bisect_left(s, s[i] * 2 - s[pre[i]])
            pre[j] = i
        return f[n]

Complexity

Pattern: Stack

When the most recent unresolved thing is the one that matters, use a stack. LeetCode 2945. Find Maximum Non-decreasing Array Length is filed here because LeetCode tags it Stack and Queue, which is the vocabulary this hub collects.

The stack guide has the Python template for the pattern and the 194 LeetCode problems that use it.

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