# Sudo Placement[1.3] | Stack Design

Given q number of queries, you need to perform operations on the stack. Queries are of three types 1, 2 and 3. If the operation is to push (1) then push the elements, if the operations is to pop (2) then pop the element and if it is Top (3), then print the element at the top of stack (If stack is empty, print “-1”, without quotes).

Examples:

```Input: Queries =  6
3
1 5
1 6
1 7
2
3
Output: -1
6
The first query is to print top, but since the stack is empty, so we print -1.
Next three queries are to push 5, 6, and 7, so we pushed them on a stack.
Next query is pop, so we popped 7 from a stack. Final query is to print the
top, so 6 is there at the top and thus printed.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Stack can be used to perform the given operation. If the input for a query is 1, then take another input and push the element into the stack using push() function. If the input for a query is 2, then pop the element using pop() function in a stack. If the input for a query is 3, then print the top element using top() function.

Below is the implemenatation of the above aprpoach:

## C++

 `// C++ program for ` `// Sudo-Placement | Stack Design ` `#include ` `using` `namespace` `std; ` ` `  `stack<``int``> s; ` ` `  `// function to perform type-1 operation ` `void` `_push(``int` `n) ` `{ ` `    ``s.push(n); ` `} ` ` `  `// function to perform type-2 operation ` `void` `_pop() ` `{ ` `    ``s.pop(); ` `} ` ` `  `// function to perform type-3 operation ` `void` `print() ` `{ ` `    ``// if the stack is not empty ` `    ``if` `(!s.empty()) ` `        ``cout << s.top() << endl; ` `    ``else` `        ``cout << -1 << endl; ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``// 1st query ` `    ``print(); ` `    ``// 2nd query ` `    ``_push(5); ` ` `  `    ``// 3rd query ` `    ``_push(6); ` ` `  `    ``// 4th query ` `    ``_push(7); ` ` `  `    ``// 5th query ` `    ``_pop(); ` ` `  `    ``// 6th query ` `    ``print(); ` ` `  `    ``return` `0; ` `} `

## Java

 `import` `java.util.*; ` `// Java program for ` `// Sudo-Placement | Stack Design ` ` `  `class` `GFG  ` `{ ` ` `  `    ``static` `Stack s = ``new` `Stack<>(); ` ` `  `    ``// function to perform type-1 operation ` `    ``static` `void` `_push(``int` `n)  ` `    ``{ ` `        ``s.push(n); ` `    ``} ` ` `  `    ``// function to perform type-2 operation ` `    ``static` `void` `_pop()  ` `    ``{ ` `        ``s.pop(); ` `    ``} ` ` `  `    ``// function to perform type-3 operation ` `    ``static` `void` `print()  ` `    ``{ ` `         `  `        ``// if the stack is not empty ` `        ``if` `(!s.empty())  ` `        ``{ ` `            ``System.out.println(s.peek()); ` `        ``}  ` `        ``else`  `        ``{ ` `            ``System.out.println(-``1``); ` `        ``} ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String[] args)  ` `    ``{ ` `        ``// 1st query ` `        ``print(); ` `        ``// 2nd query ` `        ``_push(``5``); ` ` `  `        ``// 3rd query ` `        ``_push(``6``); ` ` `  `        ``// 4th query ` `        ``_push(``7``); ` ` `  `        ``// 5th query ` `        ``_pop(); ` ` `  `        ``// 6th query ` `        ``print(); ` `    ``} ` `} ` ` `  `// This code contributed by Rajput-Ji `

## C#

 `// C# program for ` `// Sudo-Placement | Stack Design ` `using` `System; ` `using` `System.Collections.Generic; ` ` `  `class` `GFG  ` `{ ` ` `  `    ``static` `Stack<``int``> s = ``new` `Stack<``int``>(); ` ` `  `    ``// function to perform type-1 operation ` `    ``static` `void` `_push(``int` `n)  ` `    ``{ ` `        ``s.Push(n); ` `    ``} ` ` `  `    ``// function to perform type-2 operation ` `    ``static` `void` `_pop()  ` `    ``{ ` `        ``s.Pop(); ` `    ``} ` ` `  `    ``// function to perform type-3 operation ` `    ``static` `void` `print()  ` `    ``{ ` `         `  `        ``// if the stack is not empty ` `        ``if` `(s.Count != 0)  ` `        ``{ ` `            ``Console.WriteLine(s.Peek()); ` `        ``}  ` `        ``else` `        ``{ ` `            ``Console.WriteLine(-1); ` `        ``} ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `Main()  ` `    ``{ ` `        ``// 1st query ` `        ``print(); ` `        ``// 2nd query ` `        ``_push(5); ` ` `  `        ``// 3rd query ` `        ``_push(6); ` ` `  `        ``// 4th query ` `        ``_push(7); ` ` `  `        ``// 5th query ` `        ``_pop(); ` ` `  `        ``// 6th query ` `        ``print(); ` `    ``} ` `} ` ` `  `/* This code contributed by PrinciRaj1992 */`

Output:

```-1
6
```

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Improved By : Rajput-Ji, princiraj1992

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