INTERVIEW QUESTIONS C STRUCTURES IN C DETAILS

Question: How can we check whether the contents of two structure variables are same or not?

Answer:

Source: CoolInterview.com

There is no way to compare entire structure, we can only compare element by element.
example:
typedef struct{
int a;
int b;
} ravi_t;
main()
{
ravi_t r;
ravi_t s;
/* this is not allowed */
if(r==s) /* this is not allowed */;
/* where as we can compare element by element */
if(r.a == s.a); Source: CoolInterview.com

The two structure variables need to be of same type.
we can check the equality of two structure variables by comparing them individually.
example::
#include<stdio.h>
#include<conio.h>
struct student
{
int rno;
char name[20];
float tot;
}a,b;
void main()
{
clrscr();
printf("enter rno,total of student 1");
scanf("%d%f",a.rno,a.total);
printf("
enter the name of student1");
scanf("%s",a.name);
printf("
enter the rno and total of student2");
scanf("%d%f",b.rno,b.total);
printf("
enter the name of student2");
scanf("%s",b.name);

if((a.rno==b.rno)&&(a.name==b.name)&&(a.total==b.total))
printf("
two structure variables are equal");
else
printf("
two structure variables are not equal");
getch();
}
Source: CoolInterview.com

The only possible way is through by checking every element by element. Source: CoolInterview.com

One more method,

convert two structure pointer as (char *) anyway we know the size so we could compare byte by byte. Source: CoolInterview.com

use memcmp().

eg:
#include <stdio.h>
typedef struct
{
int a;
float f;
}Struct;

int
main()
{
Struct s1,s2;
s1.a = 25;
s1.f = 3.55;
s2.a = 25;
s2.f = 4.55;
if(0 == memcmp(&s1,&s2,sizeof(s1)))
{
printf("
Equal
");
}
else
printf("
Not Equal
");

getchar();
return 0;
} Source: CoolInterview.com

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