[Leet Code] Build an Array With Stack Operations

Leetcode: https://leetcode.com/problems/build-an-array-with-stack-operations/

Problem:

Given an array target and an integer n. In each iteration, you will read a number from list = {1,2,3..., n}.

Build the target array using the following operations:

• Push: Read a new element from the beginning list, and push it in the array.
• Pop: delete the last element of the array.
• If the target array is already built, stop reading more elements.

Return the operations to build the target array. You are guaranteed that the answer is unique.

Example 1:

Input: target = [1,3], n = 3
Output: ["Push","Push","Pop","Push"]
Explanation: 
Read number 1 and automatically push in the array -> [1]
Read number 2 and automatically push in the array then Pop it -> [1]
Read number 3 and automatically push in the array -> [1,3]

Example 2:

Input: target = [1,2,3], n = 3
Output: ["Push","Push","Push"]

Example 3:

Input: target = [1,2], n = 4
Output: ["Push","Push"]
Explanation: You only need to read the first 2 numbers and stop.

Example 4:

Input: target = [2,3,4], n = 4
Output: ["Push","Pop","Push","Push","Push"]

Constraints:

• 1 <= target.length <= 100
• 1 <= target[i] <= n
• 1 <= n <= 100
• target is strictly increasing.

Solution:

class Solution(object):
    def buildArray(self, target, n):
        """
        :type target: List[int]
        :type n: int
        :rtype: List[str]
        """
        result_list = []
        for i in range(1,n+1):
            if i>target[len(target)-1]:
                return result_list
            result_list.append("Push")
            if i not in target:
                result_list.append("Pop")
        return result_list