Build an Array With Stack Operations

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.

You are guaranteed that the target array is strictly increasing, only containing numbers between 1 to n inclusive.

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] <= 100

• 1 <= n <= 100

• target is strictly increasing.

class Solution {
    public List<String> buildArray(int[] target, int n) {
        List<String> ans = new ArrayList<>();
        int index = 0;
        for (int i = 1; i <= n; i++) {
            if (index == target.length)
                break;
            else if (i == target[index]) {
                index++;
                ans.add("Push");
            } else {
                ans.add("Push");
                ans.add("Pop");
            }
        }
        return ans;
    }
}