README.md

1441. 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.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn build_array(target: Vec<i32>, n: i32) -> Vec<String> {
        let mut i = 1;
        let mut ret = vec![];

        for num in target {
            for _ in 0..(num - i) {
                ret.push("Push".to_string());
                ret.push("Pop".to_string());
            }
            ret.push("Push".to_string());
            i = num + 1;
        }

        ret
    }
}