Solutions

1. Brute Force

class StockSpanner:

    def __init__(self):
        self.arr = []

    def next(self, price: int) -> int:
        self.arr.append(price)
        i = len(self.arr) - 2
        while i >= 0 and self.arr[i] <= price:
            i -= 1
        return len(self.arr) - i - 1

Time & Space Complexity

Time complexity: $O(n ^ 2)$
Space complexity: $O(n)$

Where $n$ is the number of function calls.

2. Monotonic Decreasing Stack

class StockSpanner:

    def __init__(self):
        self.stack = []  # pair: (price, span)

    def next(self, price: int) -> int:
        span = 1
        while self.stack and self.stack[-1][0] <= price:
            span += self.stack[-1][1]
            self.stack.pop()
        self.stack.append((price, span))
        return span

Time & Space Complexity

Time complexity: $O(n)$
Space complexity: $O(n)$

Where $n$ is the number of function calls.