Merge pull request #15 from arunkumarpvt/add-stack-operations

Add operations in stack

Stack/C++/stack_operations.cpp

@@ -0,0 +1,107 @@
+/*Stack is a linear data structure which follows a particular order in which the operations are performed.
+The order may be LIFO(Last In First Out) or FILO(First In Last Out).
+
+Mainly the following three basic operations are performed in the stack:
+
+1. Push: Adds an item in the stack. If the stack is full, then it is said to be an Overflow condition.
+2. Pop: Removes 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.
+3. Peek or Top: Returns top element of stack.
+isEmpty: Returns true if stack is empty, else false.
+*/
+
+
+
+/* C++ program to implement basic stack 
+   operations */
+#include <bits/stdc++.h> 
+
+using namespace std; 
+
+#define MAX 1000 
+
+class Stack { 
+    int top; 
+
+public: 
+    int a[MAX]; // Maximum size of Stack 
+
+    Stack() { top = -1; } 
+    bool push(int x); 
+    int pop(); 
+    int peek(); 
+    bool isEmpty(); 
+}; 
+
+bool Stack::push(int x) 
+{ 
+    if (top >= (MAX - 1)) { 
+        cout << "Stack Overflow"; 
+        return false; 
+    } 
+    else { 
+        a[++top] = x; 
+        cout << x << " pushed into stack\n"; 
+        return true; 
+    } 
+} 
+
+int Stack::pop() 
+{ 
+    if (top < 0) { 
+        cout << "Stack Underflow"; 
+        return 0; 
+    } 
+    else { 
+        int x = a[top--]; 
+        return x; 
+    } 
+} 
+int Stack::peek() 
+{ 
+    if (top < 0) { 
+        cout << "Stack is Empty"; 
+        return 0; 
+    } 
+    else { 
+        int x = a[top]; 
+        return x; 
+    } 
+} 
+
+bool Stack::isEmpty() 
+{ 
+    return (top < 0); 
+} 
+
+// Driver program to test above functions 
+int main() 
+{ 
+    class Stack s; 
+    s.push(10); 
+    s.push(20); 
+    s.push(30); 
+    cout << s.pop() << " Popped from stack\n"; 
+
+    return 0; 
+}
+
+
+
+
+/*
+Output :
+
+10 pushed into stack
+20 pushed into stack
+30 pushed into stack
+30 popped from stack
+*/
+
+
+
+/*
+Time Complexity:
+push(), pop(), isEmpty() and peek() all take O(1) time. 
+We do not run any loop in any of these operations.
+*/