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