1441.build-an-array-with-stack-operations.cpp

/*
 * @lc app=leetcode id=1441 lang=cpp
 *
 * [1441] Build an Array With Stack Operations
 *
 * https://leetcode.com/problems/build-an-array-with-stack-operations/description/
 *
 * algorithms
 * Easy (71.06%)
 * Likes:    500
 * Dislikes: 811
 * Total Accepted:    62.5K
 * Total Submissions: 87.9K
 * Testcase Example:  '[1,3]\n3'
 *
 * 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.
 * 
 * 
 */

// @lc code=start
class Solution {
    #include <vector>
    #include <iostream>
public:
    vector<string> buildArray(vector<int>& target, int n) {
        vector<string> ans;
        int count = 1;
        for( int i =0;i<target.size();i++){
            if (count == target[i]){
                ans.push_back("Push");
                count++;
            }else{
                while(count<target[i]){
                    if(count == n){
                        ans.push_back("Push");
                        return ans;
                    }
                    ans.push_back("Push");
                    ans.push_back("Pop");
                    count++;
                }
                ans.push_back("Push");
                count++;
            }
        }
        return ans;
    }
};
// @lc code=end