Build an Array With Stack Operations — LeetCode 1441 Python Solution

The problem

You are given an integer array target and an integer n. You have an empty stack with the two following operations: "Push": pushes an integer to the top of the stack.

Example

Input

target = [1,3], n = 3

Output

["Push","Push","Pop","Push"]

Explanation

Initially the stack s is empty. The last element is the top of the stack.

Python solution

class Solution:
    def buildArray(self, target: List[int], n: int) -> List[str]:
        ans = []
        cur = 1
        for x in target:
            while cur < x:
                ans.extend(["Push", "Pop"])
                cur += 1
            ans.append("Push")
            cur += 1
        return ans

Complexity

Pattern: Stack

When the most recent unresolved thing is the one that matters, use a stack. LeetCode 1441. Build an Array With Stack Operations 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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