CLASS NOTES FOR 9/26/02
Stack = Last one first
ADT = abstract data type (user defined data type)
Info is hidden when things are abstract.

for (int i = 0, i < 6, i++)

cin >> table[i];

 

for (i=5,i >= 0 , i--)

 

Everything is a character (every strike on a keyboard is a character) 
 

 

Assume the following:

 

23

char t;

cin.get (t)

cout <, t //will give u the value 2

 

 

 

void main()

{

int num;

char t;

cin.get(t)

if t(>=¡¯0¡¯) && (t<=¡¯9¡¯){

cin >> num;

cout << ¡°number¡±;

else cout << ¡°not number¡±;

 

// output = 3

 

 

ENTER A POSTFIX NOTATION
 

//ENTER A POSTFIX NOTATION 

 

#include<iostream.h>

void push (int stack[],int &top,int x){

            stack[top++]=x; }//push

int pop (int stack [],int &top){

            return stack [--top]; }//pop

int evaluate(int num1, int num2, char t){

            switch(t){

            case'+':return num2+num1;break;

            case'-':return num2-num1;break;

            case'/':return num2/num1;break;

            case'*':return num2*num1;break;

            }//switch 

}//evaluate

int main (){

            int stack [10],top=0,x,num1,num2,value;

            char t;

            cout<<"please enter a postfix notation"<<endl;

            while(cin.get(t)){

                        if((t>='0')&&(t<='9')){

                                    cin.putback(t);cin>>x;

                                    push(stack,top,x);}//if

                        else if ((t=='+') || (t=='-')||(t=='/')||(t=='*')){

                                    num1=pop(stack,top);

                                    num2=pop(stack,top);

                                    value=evaluate (num1,num2,t);

                                    push (stack,top,value);

                        }//else if

                        if (t=='\n') break;

            }//while

            cout<<pop(stack,top);

            return 0;

}//main

 

//OUTPUT IS 12 5 3 + *

 

 

Choice b is a better form of programming because it has structure to it.

 

Infix Evaluation
2 3 4 * +

Algorithm = If digit then PUSH

                                else

                                if operator 

                                pop 

                                pop

                                evaluate

                                push

                                else no more, pop

                                DISPLAY

 

How would make a stack?
Array
176 786 664 

 

0 1 2 3

 

Stack
number [0] = 176

number [1] = 786

number [2] = 664

number [i] 

                i++;

stack [i]

                i++;

 

change i to top

 

stack[top] = X

top++;

 

1)       1)       Write a function called Push?

Int stack [10];

Int top = 0;

Int x;

Push (){

Stack [top] = x

Top++;

}

main()

{

push();

}//main

 

2)       2)       2 ways to use stack are Array and Pointer

SIMPLE STACK MENU
 

#include<iostream.h>

void push (int mystack[],int & mytop,int item){

        mystack[mytop]=item;

        mytop=mytop+1;} //PUSH

int pop(int mystack[],int &mytop){

        mytop=mytop-1;

        int item=mystack[mytop];

        return item; }//POP

int isempty(int mytop){

        if(mytop==0) return 1;

        else return 0;}//ISEMPTY

int isfull(int mytop,const int MAXSTACKSIZE){

        if(mytop==MAXSTACKSIZE)return 1;

        else return 0;}//ISFULL

void main(){

        const int MAXSTACKSIZE=5;

        int mystack[MAXSTACKSIZE];int mytop,x,option;

        mytop=0;//STACK TOP INITILIZATION

        do{cout<<"SELECT ONE OF THE FOLLOWING OPTIONS:"<<endl;

        cout<<"1-PUSH 2-POP 3-EMPTY 4-ISFULL 5-QUIT:";

        cin>>option;

        switch(option){

        case 1: if (isfull(mytop,MAXSTACKSIZE))

                                                        cout<<"YOU CANT PUSH"<<endl;

                        else{ cout<<"ENTER THE NUMBER THAT WILL BE PUSHED:";

                                                        cin>>x;

                                                        push(mystack,mytop,x);}//ELSE

                        break;

        case 2: if(isempty(mytop))

                                                        cout<<"YOU CANT POP"<<endl;

                        else{ cout<<"THE NUMBER POOPED IS:"<<pop(mystack,mytop);

                        cout<<endl;}//ELSE

                        break;

        case 3: if(isempty(mytop)==1)

                                                        cout<<"STACK EMPTY."<<endl;

                        else cout<<"STACK IS NOT EMPTY."<<endl;

                        break;

        case 4: if(isfull(mytop, MAXSTACKSIZE)==1)

                                                                        cout<<"STACK FULL."<<endl;

                        else cout<<"STACK IS NOT FULL."<<endl;

                        break;

        case 5: cout<<"THANK YOU FOR USING OUR MENU!"<<endl;

                        break;

        default:cout <<"ENTER CORRECT OPTIONS"<<endl;}//switch

        }while (option !=5);

}//MAIN