In order to make manipulations in a stack, there are certain operations provided to us for Stack, which include:
- push() to insert an element into the stack
- pop() to remove an element from the stack
- top() Returns the top element of the stack.
- isEmpty() returns true if the stack is empty else false.
- size() returns the size of the stack.
In this post, we will see how to perform these operations on Stack.
Push Operation in Stack:
Push operation adds an item to the stack.
If the stack is full, then it is said to be an Overflow condition.
Below is a sample program to show Push operation in Stack.
C++
#include <bits/stdc++.h> using namespace std; int main() { stack<int> s; // creating a stack of integers s.push(1); // This pushes 1 to the stack top s.push(2); // This pushes 2 to the stack top s.push(3); // This pushes 3 to the stack top s.push(4); // This pushes 4 to the stack top s.push(5); // This pushes 5 to the stack top // printing the stack while (!s.empty()) { cout << s.top() << " "; s.pop(); } // The above loop prints "5 4 3 2 1" } |
Python3
# Python Code:stack = []stack.append(1) # This pushes 1 to the stack topstack.append(2) # This pushes 2 to the stack topstack.append(3) # This pushes 3 to the stack topstack.append(4) # This pushes 4 to the stack topstack.append(5) # This pushes 5 to the stack top# printing the stackwhile stack: print(stack[-1], end=" ") stack.pop()# The above loop prints "5 4 3 2 1"# This code is contributed by Sakshi |
Output
5 4 3 2 1
Pop Operation in Stack:
Pop operation is used to remove an item from the stack.
The items are popped in the reversed order in which they are pushed. If the stack is empty, then it is said to be an Underflow condition.
Below is a sample program to show Pop operation in Stack.
C++
#include <bits/stdc++.h> using namespace std; int main() { stack<int> s; // creating a stack of integers s.push(1); // This pushes 1 to the stack top s.push(2); // This pushes 2 to the stack top s.push(3); // This pushes 3 to the stack top s.push(4); // This pushes 4 to the stack top s.push(5); // This pushes 5 to the stack top // printing the stack while (!s.empty()) { cout << s.top() << " "; s.pop(); } // The above loop prints "5 4 3 2 1" // Now, let us remove elements from the stack using pop // function s.pop(); // removes 5 from the stack since 5 was present // at the top. Now, the new stack top // becomes 4. s.pop(); // removes 4 from the stack since 4 was present // at the top. Now, the new stack top // becomes 3. s.pop(); // removes 3 from the stack since 3 was present // at the top. Now, the new stack top // becomes 2. s.pop(); // removes 2 from the stack since 2 was present // at the top. Now, the new stack top // becomes 1. s.pop(); // removes 1 from the stack since 1 was present // at the top. Now, the stack becomes empty. } |
Python3
# Python Code:stack = []stack.append(1) # This pushes 1 to the stack topstack.append(2) # This pushes 2 to the stack topstack.append(3) # This pushes 3 to the stack topstack.append(4) # This pushes 4 to the stack topstack.append(5) # This pushes 5 to the stack top# Now, let us remove elements from the stack using pop# functionprint(stack[-1], end=" ")stack.pop() # removes 5 from the stack since 5 was present # at the top. Now, the new stack top # becomes 4.print(stack[-1], end=" ")stack.pop() # removes 4 from the stack since 4 was present # at the top. Now, the new stack top # becomes 3. print(stack[-1], end=" ")stack.pop() # removes 3 from the stack since 3 was present # at the top. Now, the new stack top # becomes 2. print(stack[-1], end=" ")stack.pop() # removes 2 from the stack since 2 was present # at the top. Now, the new stack top # becomes 1. print(stack[-1], end=" ")stack.pop() # removes 1 from the stack since 1 was present # at the top. Now, the stack becomes empty. # This code is contributed by Sakshi |
Output
5 4 3 2 1
Top Operation in Stack:
Top operation is used to return the top element of the stack.
Below is a sample program to show Pop operation in Stack.
C++
#include <bits/stdc++.h> using namespace std; int topElement(stack<int>& s) { return s.top(); } int main() { stack<int> s; // creating a stack of integers s.push(1); // This pushes 1 to the stack top cout << topElement(s) << endl; // Prints 1 since 1 is present at the // stack top s.push(2); // This pushes 2 to the stack top cout << topElement(s) << endl; // Prints 2 since 2 is present at the // stack top s.push(3); // This pushes 3 to the stack top cout << topElement(s) << endl; // Prints 3 since 3 is present at the // stack top } |
Python3
# Python code:def topElement(s): return s[-1]s = [] # creating a stack of integerss.append(1) # This pushes 1 to the stack topprint(topElement(s)) # Prints 1 since 1 is present at the stack tops.append(2) # This pushes 2 to the stack topprint(topElement(s)) # Prints 2 since 2 is present at the stack tops.append(3) # This pushes 3 to the stack topprint(topElement(s)) # Prints 3 since 3 is present at the stack top# This code is contributed by Sakshi |
Output
1 2 3
isEmpty Operation in Stack:
isEmpty operation is a boolean operation that is used to determine if the stack is empty or not.
This operation will return true if the stack is empty, else false.
Below is a sample program to show Pop operation in Stack.
C++
#include <bits/stdc++.h> using namespace std; bool isEmpty(stack<int>& s) { bool isStackEmpty = s.empty(); // checking whether stack is empty or // not and storing it into isStackEmpty // variable return isStackEmpty; // returning bool value stored in // isStackEmpty } int main() { stack<int> s; // The if - else conditional statements below prints // "Stack is empty." if (isEmpty(s)) { cout << "Stack is empty." << endl; } else { cout << "Stack is not empty." << endl; } s.push(1); // Inserting value 1 to the stack top // The if - else conditional statements below prints // "Stack is not empty." if (isEmpty(s)) { cout << "Stack is empty." << endl; } else { cout << "Stack is not empty." << endl; } } |
Python3
# Python Code:def isEmpty(s): isStackEmpty = len(s) == 0 # checking whether stack is empty or # not and storing it into isStackEmpty variable return isStackEmpty # returning bool value stored in isStackEmptys = []# The if - else conditional statements below prints "Stack is empty."if isEmpty(s): print("Stack is empty.")else: print("Stack is not empty.")s.append(1) # Inserting value 1 to the stack top# The if - else conditional statements below prints "Stack is not empty."if isEmpty(s): print("Stack is empty.")else: print("Stack is not empty.") # This code is contributed by Sakshi |
Output
Stack is empty. Stack is not empty.
size() Operation in Stack:
Size operation in Stack is used to return the count of elements that are present inside the stack.
Below is a sample program to show Pop operation in Stack.
C++
#include <bits/stdc++.h> using namespace std; int main() { stack<int> s; // creating a stack of integers cout << s.size() << endl; // Prints 0 since the stack is empty s.push(1); // This pushes 1 to the stack top s.push(2); // This pushes 2 to the stack top cout << s.size() << endl; // Prints 2 since the stack // contains two elements s.push(3); // This pushes 3 to the stack top cout << s.size() << endl; // Prints 3 since the stack // contains three elements } |
Python3
# PYthon Code:stack = [] # creating an empty list as a stackprint(len(stack)) # Prints 0 since the stack is emptystack.append(1) # This appends 1 to the stackstack.append(2) # This appends 2 to the stackprint(len(stack)) # Prints 2 since the stack contains two elementsstack.append(3) # This appends 3 to the stackprint(len(stack)) # Prints 3 since the stack contains three element# This code is contributed by Sakshi |
Output
0 2 3
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