Stacks and queues are data structures that store elements of a specific data type. They have various operations (methods/functions) to input, output and manage the data.
Stack implements a last-in, first-out (LIFO) policy on its elements. So, the element removed from the stack is always the most recently inserted one. On the other hand, Queue implements first-in, first-out (FIFO) policy on its elements. Hence in a queue, the deleted element is always the element that has been inserted for the longest time.
Stack
These are the operations provided for a stack:
Stack-Empty (S) 1. if S.empty() == true 2. return true 3. else 4. return false Push (S, x) 1. S.size() = S.size() + 1 2. S.push(x) Pop (S) 1. if Stack-Empty (S) 2. return NULL 3 else 4. x = S.top() 5 S.size() = S.size() - 1 6. S.pop() 7. return x
Code Implementation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 | //// main.cpp// Stack//// Created by Himanshu on 03/10/21.//#include <iostream>#include <stack>using namespace std;int main () { stack<int> st; cout<<"Push(x) {10, 20, 30, 40, 50}"<<endl; st.push(10); st.push(20); st.push(30); st.push(40); st.push(50); cout<<"Stack-Empty(): "; if (st.empty()) { cout<<"Stack is empty"<<endl; } else { cout<<"Stack is not empty"<<endl; } cout<<"Pop elements..."<<endl; while (!st.empty()) { cout<< st.top()<<" "; st.pop(); } cout<<endl; cout<<"Stack-Empty(): "; if (st.empty()) { cout<<"Stack is empty"<<endl; } else { cout<<"Stack is not empty"<<endl; } return 0;} |
Output
Push(x) {10, 20, 30, 40, 50}
Stack-Empty(): Stack is not empty
Pop elements...
50 40 30 20 10
Stack-Empty(): Stack is empty
Here’s a working example: C++ STL Stack
Queue
These are the operations provided for a queue:
Queue-Empty (Q) 1. if Q.empty() == true 2. return true 3. else 4. return false Enqueue (Q, x) 1. Q.size() = Q.size() + 1 2. Q.push(x) Dequeue (Q) 1. if Queue-Empty (Q) 2. return NULL 3 else 4. x = Q.front() 5 Q.size() = Q.size() - 1 6. Q.pop() 7. return x
Code Implementation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | //// main.cpp// Queue//// Created by Himanshu on 03/10/21.//#include <iostream>#include <queue>using namespace std;int main () { queue<int> qu; cout<<"Enqueue(x) {10, 20, 30, 40, 50}"<<endl; qu.push(10); qu.push(20); qu.push(30); qu.push(40); qu.push(50); cout<<"Queue-Empty(): "; if (qu.empty()) { cout<<"Queue is empty"<<endl; } else { cout<<"Queue is not empty"<<endl; } cout<<"Dequeue elements..."<<endl; while (!qu.empty()) { cout<<qu.front()<<" "; qu.pop(); } cout<<endl; cout<<"Queue-Empty(): "; if (qu.empty()) { cout<<"Queue is empty"<<endl; } else { cout<<"Queue is not empty"<<endl; } return 0;} |
Output
Enqueue(x) {10, 20, 30, 40, 50}
Queue-Empty(): Queue is not empty
Dequeue elements...
10 20 30 40 50
Queue-Empty(): Queue is empty
Here’s a working example: C++ STL Queue