Word Machine SOLUTIONS Weekly Contest 25

You are given elite of strings operations where every component is either: 

 

A non-negative number that ought to be driven into a stack 

 

“POP” which means pop the top component in the stack 

 

“DUP” which means copy the top component in the stack 

 

“+” which means pop the best two and push the whole 

 

“- ” which means pop the best two and push top – second 

 

Return the top component in the stack subsequent to applying all activities. In the event that there are any invalid tasks, return – 1. 

 

Requirements 

 

n ≤ 100,000 where n is the length of operations 

 

Model 1 

 

Information 

 

operations = [“1”, “5”, “DUP”, “3”, “- “] 

 

Yield 

 

– 2 

 

Clarification 

 

Following the activities: 

 

We drive 1 into the stack: [1] 

 

We drive 5 into the stack: [1, 5] 

 

We copy the top component: [1, 5, 5] 

 

We drive 3 into the stack: [1, 5, 5, 3] 

 

We pop 3 and 5 and push their distinction 3 – 5: [1, 5, – 2] 

 

We return the top component which is – 2 

 

Model 2 

 

Information 

 

operations = [“+”] 

 

Yield 

 

– 1 

 

Clarification 

 

There’s no components in the stack so this is invalid.