Design a Stack With Increment Operation — LeetCode 1381 Python Solution

The problem

Design a stack that supports increment operations on its elements. Implement the CustomStack class: CustomStack(int maxSize) Initializes the object with maxSize which is the maximum number of elements in the stack.

Example

Input

["CustomStack","push","push","pop","push","push","push","increment","increment","pop","pop","pop","pop"]

Output

[null,null,null,2,null,null,null,null,null,103,202,201,-1]

Explanation

CustomStack stk = new CustomStack(3); // Stack is Empty []

Python solution

class CustomStack:
    def __init__(self, maxSize: int):
        self.stk = [0] * maxSize
        self.add = [0] * maxSize
        self.i = 0

    def push(self, x: int) -> None:
        if self.i < len(self.stk):
            self.stk[self.i] = x
            self.i += 1

    def pop(self) -> int:
        if self.i <= 0:
            return -1
        self.i -= 1
        ans = self.stk[self.i] + self.add[self.i]
        if self.i > 0:
            self.add[self.i - 1] += self.add[self.i]
        self.add[self.i] = 0
        return ans

    def increment(self, k: int, val: int) -> None:
        i = min(k, self.i) - 1
        if i >= 0:
            self.add[i] += val


# Your CustomStack object will be instantiated and called as such:
# obj = CustomStack(maxSize)
# obj.push(x)
# param_2 = obj.pop()
# obj.increment(k,val)

Complexity

Pattern: Stack

When the most recent unresolved thing is the one that matters, use a stack. LeetCode 1381. Design a Stack With Increment Operation is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Stack.

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

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