Leetcode 1381. 设计一个支持增量操作的栈

class CustomStack:

    def __init__(self, maxSize: int):
        self.arr = []
        self.maxSize = maxSize

    def push(self, x: int) -> None:
        if len(self.arr) < maxSize:
            self.arr.append(x)

    def pop(self) -> int:
        if self.arr:
            return self.arr.pop()
        else:
            return -1


    def increment(self, k: int, val: int) -> None:
        if not self.arr:
            return
        elif len(self.arr) <= k:
            for i in range(len(self.arr)):
                self.arr[i] += val
        else:
            for i in range(k):
                self.arr[i] += val