Problem URL: 132 pattern

We will use a stack to store the numbers. Then, we will iterate through the numbers and check if the number is less than the second number. If it is, then we will pop the numbers from the stack until the number is less than the second number. Then, we will check if the number is less than the third number. If it is, then we will return true. If it is not, then we will push the number to the stack. If we reach the end of the loop, then we will return false.

class Solution:
    def find132pattern(self, nums: List[int]) -> bool:
        stack = []
        second = -math.inf

        for num in nums[::-1]:
            if num < second:
                return True
            while stack and num > stack[-1]:
                second = stack.pop()
            stack.append(num)

        return False

Time Complexity: O(n), n is the length of the given array.
Space Complexity: O(n)