build-an-array-with-stack-operations

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1441. Build an Array With Stack Operations (Easy)

You are 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": Reads a new element from the beginning list, and pushes it in the array.
• "Pop": Deletes the last element of the array.
• If the target array is already built, stop reading more elements.

Return a list of the operations needed to build target. The test cases are generated so 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.

 

Constraints:

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

Related Topics

[Array] [Stack] [Simulation]

Hints

Hint 1

Use “Push” for numbers to be kept in target array and [“Push”, “Pop”] for numbers to be discarded.