Implementing stack

Implementing stack

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  Prepared by Mohammed Sikander TechnicalLead Cranes Software International Limited
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  This document willhelp you to understand the concepts of C++ through simple programs.The topics covered in this document are  Size of Class  Constructor and Destructor  Lifetime of Objects  Memory Leakage mohammed.sikander@cranessoftware.com 2
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  C int buffer[20]; int topIndex= -1; void push(int ele); int pop( ); void display( ); DRAWBACKOFTHIS APPROACH  This approach works only if you have One stack in the program. Sikander 3
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  WORKWITH LOCALVARIABLES AND PARAMETERS voidpush(int buffer[],int *ti,int ele); int pop(int buffer[],int *ti); void display(const int buffer[],int ti); int main( ) { int buffer1[20] , buffer2[20]; int ti1 =-1 , ti2 = -1; //Insert in first Stack. push(buffer1, &ti1 , 45); //Insert in Second Stack push(buffer2, &ti2 , 75); } DRAWBACKOFTHIS APPROACH  Every time you want to add a new stack, we need to create two separate variables (Array andTopIndex)  Possibility of passing buffer1 and ti2. Sikander 4
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  GROUP BUFFER ANDTOPINDEX INTO ONE UNIT struct MyStack { int ti; int buffer[20]; }; void push(MyStack *ps,int ele) { buffer[++ti] = ele; ps->buffer[++ps->ti] = ele; } int pop(MyStack *ps); void display(const MyStack *ps); int main( ) { struct MyStack s1 = {-1} , s2 = {-1}; //Insert in first Stack. push( &s1 , 45); //Insert in Second Stack push(&2 , 75); } Sikander 5
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  GROUPING DATA ANDFUNCTIONS INTO ONE UNIT struct MyStack { int ti; int buffer[20]; void push(int ele) { buffer[++ti] = ele; } }; int main( ) { MyStack s1 = {-1} , s2 = {-1}; s1.push(45); s2.push( 75); } Sikander 6
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  • All membersare private by default in class. • Cannot access private members from outside the class. • Cannot initialize the members of class / struct with traditional method if the members are private class MyStack { int ti; int buffer[20]; void push(int ele) { buffer[++ti] = ele; } }; int main( ) { MyStack s1 = {-1} , s2 = {-1}; s1.push(45); s2.push( 75); } Sikander 7
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  • All membersare private by default in class. • Cannot access private members from outside the class. • Cannot initialize the members of class / struct with traditional method if the members are private class MyStack { int ti; int buffer[20]; public: void push(int ele) { buffer[++ti] = ele; } }; int main( ) { MyStack s1, s2; s1.push(45); s2.push( 75); } Sikander 8
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  • What happensif we forget to invoke initialize function? • Can we write a function such that it invokes automatically on Object Creation? class MyStack { int ti; int buffer[20]; public: void initialize( ) { ti = -1; } void push(int ele); }; int main( ) { MyStack s1, s2; s1.initialize( ); s2.initialize( ); s1.push(45); s2.push( 75); } Sikander 9
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  class MyStack { int ti; intbuffer[20]; public: MyStack( ) { ti = -1; } void push(int ele) { if(top == 20-1) cout <<“Stack Full”; else buffer[++topIndex] = ele; } }; int main( ) { MyStack s1, s2; s1.push(45); s2.push( 75); } Sikander 10
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  mystack.cpp #include“mystack.h” MyStack::MyStack( ) { ti= -1; } void MyStack::push(intele) { buffer[++ti] = ele; } int MyStack::pop() { return buffer[ti--]; } Testmystack.cpp #include “mystack.h” int main( ) { MyStack s1; s1.push(45); s1.push( 75); cout << s1.pop( ) << endl; cout << s1.pop( ) << endl; } Sikander 11 mystack.h class MyStack { int ti; int buffer[20]; public: MyStack( ); void push(int ele); int pop(); };
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  class MyStack { int ti; intbuffer[20]; public: MyStack( ); void push(int ele); int pop(); void display(); }; int main( ) { MyStack s1, s2; } Sikander 12 S1 can store 20 elements. S2 can store 20 elements. Requirement : I would like to have a say on the size of buffer when creating object. Different Objects might have different sizes.
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  class MyStack { int topIndex; int*buffer; int size; public: MyStack(int sz) { topIndex = -1; size = sz; buffer = new int[size]; } void push(int ele) { if(top == size -1) cout <<“Stack Full”; else buffer[++topIndex] = ele; } }; int main( ) { //Create a stack object whichcan hold 5 elements. MyStack s1 = MyStack(5); //Create a stack object whichcan hold 10 elements. MyStack s2 = MyStack(10); cout <<“Inserting in first Stack n”; for(int index = 0 ; index < 7 ; index++) s1.push(3); cout <<“ Inserting in Second Stack n”; for(int index = 0 ; index < 7 ; index++) s2.push(5); } Sikander 13
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  Creating object withbelow statement throw error. MyStack s3; mohammed.sikander@cranessoftware.com 14 If the user does not specify the size, it should take a fixed size of 6 MyStack(int sz = 6) { topIndex = -1; size = sz; buffer = new int[size]; }
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  class MyStack { int topIndex; int*buffer; int size; public: MyStack(int sz = 6) { topIndex = -1; size = sz; buffer = new int[size]; } void push(int ele) { buffer[++topIndex] = ele; } int pop( ) { return buffer[topIndex --]; } }; int main( ) { //Create a stack object whichcan hold 5 elements. MyStack s1 = MyStack(5); cout <<“Inserting in Stack n”; for(int index = 0 ; index < 5 ; index++) s1.push(3); cout <<“Deleting from Stack n”; for(int index = 0 ; index < 5 ; index++) s1.pop( ); } Sikander 15
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  class MyStack { int topIndex; int*buffer; int size; public: MyStack(int sz = 6) ; void push(int ele); int pop( ); ~MyStack( ) { delete [ ] buffer; } }; int main( ) { //Create a stack object whichcan hold 5 elements. MyStack s1 = MyStack(5); cout <<“Inserting in Stack n”; for(int index = 0 ; index < 5 ; index++) s1.push(3); cout <<“Deleting from Stack n”; for(int index = 0 ; index < 5 ; index++) s1.pop( ); } Sikander 16
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  class MyStack { int topIndex; int*buffer; int size; public: MyStack(int sz = 6) ; void push(int ele); int pop( ); ~MyStack( ) { delete [ ] buffer; } }; int main( ) { //Create a stack object whichcan hold 5 elements. MyStack *ptr; ptr = new MyStack(5); cout <<“Inserting in Stack n”; for(int index = 0 ; index < 5 ; index++) ptr->push(3); cout <<“Deleting from Stack n”; for(int index = 0 ; index < 5 ; index++) ptr->pop( ); } Sikander 17
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  class MyStack { int topIndex; int*buffer; int size; public: MyStack(int sz = 6) ; void push(int ele); int pop( ); ~MyStack( ) { delete [ ] buffer; } }; int main( ) { //Create a stack object whichcan hold 5 elements. MyStack *ptr; ptr = new MyStack(5); cout <<“Inserting in Stack n”; for(int index = 0 ; index < 5 ; index++) ptr->push(3); cout <<“Deleting from Stack n”; for(int index = 0 ; index < 5 ; index++) ptr->pop( ); delete ptr; } Sikander 18