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Thursday, September 26, 2013
Design, develop and execute a program in C to Evaluate a valid postfix expression using stack. Assume that the postfix expression is read as a single line consisting of non-negative single digit operands and binary arithmetic operators. The arithmetic operators are +(add),-(subtract),*(multiply) and / (divide)
#include<stdio.h>
#include<conio.h>
#include<ctype.h>
#include<math.h>
char postfix[20];
int top=-1;
float value[20],stack[20];
float eval();
void push(float);
float pop();
void main()
{
int i=0;
float result;
clrscr();
printf("enter a valid postfix expression\n");
scanf("%s",postfix);
while(postfix[i]!='\0')
{
if(isalpha(postfix[i]))
{
printf("enter the value of %c\n",postfix[i]);
scanf("%f",&value[i]);
}
i++;
}
result=eval();
printf("the value of the expression is %.2f\n",result);
getch();
}
float eval()
{
int i=0;
float op1,op2,result;
while(postfix[i]!='\0')
{
if(isalpha(postfix[i]))
push(value[i]);
else
{
op2=pop();
op1=pop();
switch(postfix[i])
{
case'+':
push(op1+op2);
break;
case'-':
push(op1-op2);
break;
case'*':
push(op1*op2);
break;
case'/':
push(op1/op2);
break;
};
}
i++;
}
result=pop();
return result;
}
void push(float value)
{
top=top+1;
stack[top]=value;
return;
}
float pop()
{
return stack[top--];
}
Screenshot:
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1 comments:
algorithm?
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