Computer Programming: Two Stacks in an Array

10. Program for implementing two Stacks in an array?

Algorithm

Globally,Define MAX as 5;Declare stack[MAX],top1=-1,top2=MAX,item.

Step 1:Start

Step 2:Declare variable ch.

Step3:while(ch==’1’) repeat steps 3.1 to 3.8

3.1)Print the Menu 1.Push1 2.Push2 3.Pop1 4.Pop2 5.Display

3.2)Input and read the choice,ch.

3.3)If ch==1 then call the function push1().

3.4)Else if ch==2 then call the function push2().

3.5)Else if ch==3 then call the function pop1().

3.6)Else if ch==4 then call the function pop2().

3.7)Else if ch==5 then call the function display().

3.8)Else print “invalid key pressed”.

Step 4:End while.

Step 5:Stop.

Function push1()

Step 1:If(top1=top2-1) then

1.1)print STACK OVERFLOW.

Step 2:Else

2.1)Input and read the element to be inserted,item.

2.2)Increment ‘top1’ by 1.

2.3)Assign stack[top1]=item.

Step 3:End if

Step 4:Return.

Function push1()

Step 1:If(top1=top2-1) then

1.1)print STACK OVERFLOW.

Step 2:Else

2.1)Input and read the element to be inserted,item.

2.2)Decrement ‘top2’ by 1.

2.3)Assign stack[top2]=item.

Step 3:End if

Step 4:Return.

Function pop1()

Step 1:If (top1=-1) then

1.1)Print STACK UNDERFLOW.

Step 2:Else

2.1)Print the popped element,stack[top1].

2.2)Decrement ‘top1’ by 1.

Step 3:End if.

Step 4:Return.

Function pop2()

Step 1:If (top2=MAX-1) then

1.1)Print STACK UNDERFLOW.

Step 2:Else

2.1)Print the popped element,stack[top2].

2.2)Increment ‘top2’ by 1.

Step 3:End if.

Step 4:Return.

Function display()

Step 1:Declare variable i.

Step 2:Initialize i as 0.

Step 3:while(i<=top1) repeat steps 3.1 and 3.2

3.1)Print the elements of stack1,stack[i].

3.2)Increment i by 1.

Step 4:End while.

Step 5:Initialize i as MAX-1.

Step 6:while(i>=top2) repeat steps 6.1 and 6.2

6.1)Print the elements of stack2,stack[i].

6.2)Decrement i by 1.

Step 7:End while.

Step 8:Return.

Program

#include<stdio.h>

#include<conio.h>

#define MAX 5

char stack[MAX];

int top1=-1,top2=MAX,item;

void push1()

{

if(top1==top2-1)

printf("\nOverflow");

else

{

printf("\nEnter item\t");

scanf("%d",&item);

top1++;

stack[top1]=item;

}

void push2()

{

if(top1==top2-1)

printf("\nOverflow");

else

{

printf("\nEnter the item\t");

scanf("%d",&item);

top2--;

stack[top2]=item;

}

void pop1()

{

if(top1==-1)

printf("\nUnderflow");

else

{

printf(“The popped element is %d\n”,stack[top1]);

top1--;

}

void pop2()

{

if(top2==MAX-1)

printf("\nUnderflow\n");

else

{

printf(“The popped element is %d\n”,stack[top2]);

top2++;

}

void display()

{

int i;

printf("\nElements of stack1 are\n ");

for(i=0;i<=top1;i++)

{

printf("%d \t",stack[i]);

}

printf("\nElements of stack2 are\n ");

for(i=MAX-1;i>=top2;i--)

{

printf("%d\t ",stack[i]);

}

void main()

{

int ch;

clrscr();

do{

printf("1.Push1\t2.Push2\t3.Pop1\t4.Pop2\t5.Display\n");

scanf("%d",&ch);

switch(ch)

{

case 1:

push1();

break;

case 2:

push2();

break;

case 3:

pop1();

break;

case 4:

pop2();

break;

case 5:

display();

break;

default:

printf(“Invalid Key Pressed\n”);

}

printf("\nPress 1 to continue\n");

scanf("%d",&ch);

}while(ch==1);

getch();

}

Output