1. POSTFIX EVALUATION (I got this problem in the entrance exam of IIIT-A)
#include
#include <conio.h>
#include <stdio.h>
#include <ctype.h>
float a[30],top=-1;
void push(int val)
{
if(top==29)
cout<<"\nOVERFLOW";
else
{
top++;
a[top]=val;
}
}
void pop(char c)
{ float temp;
switch(c)
{
case '+': temp=a[top-1]+a[top];top--;a[top]=temp;break;
case '-': temp=a[top-1]-a[top];top--;a[top]=temp;break;
case '*': temp=a[top-1]*a[top];top--;a[top]=temp;break;
case '/': temp=a[top-1]/a[top];top--;a[top]=temp;break;
}
}
void main()
{ char *p=NULL; int i,s=0; char opt;
do
{ top=-1;
clrscr();
cout<<"\nENTER THE POSTFIX NOTATION(separate operator and operand by a space) : ";
gets(p);
for(i=0;p[i]!=NULL;i++)
{
if(p[i]==' ')
continue;
else if(isdigit(p[i]))
{ while(isdigit(p[i]))
{
s=s*10+p[i]-'0';
i++;
}
push(s);
s=0;
}
else
pop(p[i]);
}
cout<<"\nANS IS : "<<a[0];
cout<<"\n\nDO YOU WANT TO CONTINUE(y/n) : ";
cin>>opt;
}while(opt=='y'||opt=='Y');
getch();
}
2. CHECKING THE BALANCE OF THE PARENTHESIS (I got this problem as a lab test)
#include<iostream.h>
#include<conio.h>
#include<stdio.h>
void push(char p)
{
if(top==29)
cout<<"overflow";
else
{top++;
a[top]=p;
}
}
pop(char p)
{
switch(p)
{
case ')' : if(a[top]=='('){top--;return 1;}
case '}' : if(a[top]=='{'){top--;return 1;}
case ']' : if(a[top]=='['){top--;return 1;}
}
return 0;
}
void main()
{ char *p=NULL;int i,valid=1;char opt='y';
do
{top=-1; clrscr(); valid=1;
cout<<"\n\nENTER THE INFIX EXPRESSION : ";
gets(p);
for(i=0;p[i]!=NULL;i++)
{
if(p[i]=='('||p[i]=='{'||p[i]=='[')
push(p[i]);
else if(p[i]==')'||p[i]=='}'||p[i]==']')
{
int chk=pop(p[i]);
if(chk==0)
{valid=0;break;}
}
else
continue;
}
if(valid==1 && top==-1)
cout<<"\nbrackets are balanced" ;
else
cout<<"\nbrackets are not balanced";
cout<<"\n\ndo you wan to test more(y/n) : ";
cin>>opt;
}while(opt=='y'||opt=='Y');
getch();
}
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coding is correct but it can be optimized.....
ReplyDeleteThis is mine. Smaller and concise. :P
ReplyDelete#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 100
int stack[20], b=0;
void push(int a){
printf("Pushing %d at position %d\n",a,b);
stack[b]=a;
b++;
}
int pop(){
printf("Popping %d from position %d and setting stack top to position %d\n", stack[b-1], b-1, b-1);
b--;
return stack[b];
}
void operate(char c){
int temp1, temp2;
switch(c){
case '+':
temp1=pop();
temp2=pop();
printf("Adding %d to %d and going to push result %d\n", temp1, temp2, temp2+temp1);
push((temp2+temp1));
break;
case '-':
temp1=pop();
temp2=pop();
printf("Subtracting %d from %d and going to push result %d\n", temp1, temp2, temp2-temp1);
push((temp2-temp1));
break;
case '*':
temp1=pop();
temp2=pop();
printf("Multiplying %d by %d and going to push result %d\n", temp1, temp2, temp2*temp1);
push((temp2*temp1));
break;
case '/':
temp1=pop();
temp2=pop();
printf("Dividing %d into %d and going to push result %d\n", temp2, temp1, temp2/temp1);
push((temp2/temp1));
break;
}
}
int main(){
char *s;
s=(char *)malloc(MAX*(sizeof(char)));
fgets(s, MAX, stdin);
char *p, *q[20];
int i=0;
p = strtok(s, " ");
do{
q[i] = p;
p = strtok(NULL, " ");
i++;
}while(p!=NULL);
int j;
for(j=0;j<i;j++){
//printf("%d: %s\n",j,q[j]);
if(isdigit(*q[j])){
printf("Found %d as a number, pushing it to stack.\n",atoi(q[j]));
push(atoi(q[j]));
}
else{
printf("Found %c as an operator. Going to operate.\n",*q[j]);
operate(*q[j]);
}
}
printf("The result is: %d\n",stack[0]);
return(0);
}
@prab yur code has 3 errors if compiled as .c file and 1 error if compiled as .cpp file
ReplyDelete"ctype.h" header file include karna bhool gaya;)...waise mast code hai yaar.....aadhe se jada code to samajh heee nhe aaya...new fns use kiye hain tune..gud job:)
ReplyDeleteAbe gcc se compile kar. 20 saal purana compiler, Turbo C use karega toh yahee hoga.
ReplyDelete@prab even visual studio is rejectng to compile this mr tech addict
ReplyDeletethis doesnt handle decimals ;(
ReplyDeletewell, the original post does, but when i try to compile i get like 9 errors for "illegal use of floating point in function main"
ReplyDeletepost yur code here
ReplyDelete