Why is my C program not showing any output in the terminal when I try to find the youngest person's age among three given ages?

Question

the terminal is showing no output (blank)

// if the ages of 3 people are put telling which one is youngest//

#include<stdio.h>

int main()
{
    int a1,a2,a3;

    printf("enter the age of ram,shyam and ajay");
    scanf("%d,%d,%d",&a1,&a2,&a3);

    if(a1>a2>a3)
        printf("%d,%d,%d",a1,a2,a3);
    if(a3>a2>a1)
        printf("%d,%d,%d",a3,a2,a1);
    if(a2>a1>a3)
        printf("%d,%d,%d",a2,a1,a3);
    if(a2>a3>a1)
        printf("%d,%d,%d",a2,a3,a1);
    if(a1>a3>a2)
        printf("%d,%d,%d",a1,a3,a2);
    if(a3>a1>a2)
        printf("%d,%d,%d",a3,a1,a2);

    return 0;
}

i am not sure if you should write 3 expressions in an if statement like 1>2>3 please correct me if i am wrong

Answer 1

The line

if(a1>a2>a3)

will not do what you want. According to the rules of operator precedence and associativity, that expression is equivalent to the following:

if ( (a1>a2) > a3 )

The sub-expression (a1>a2) will evaluate to either 0 (false) or 1 (true). Therefore, the entire expression is equivalent to either

if ( 0 > a3 )

or:

if ( 1 > a3 )

What you want is instead the following:

if ( ( a1 > a2 ) && ( a2 > a3 ) )

Because the && operator has lower precedence than the > operator according to the rules mentioned above, you can write this without the parentheses:

if ( a1 > a2 && a2 > a3 )

Another problem in your solution is that if all 3 input values are identical, then none of the if statements will be true, and your program will print nothing.

I suggest that you rewrite your logic like this:

#include <stdio.h>

int main( void )
{
    int a1, a2, a3;

    printf( "Enter the age of ram,shyam and ajay: " );
    scanf( "%d,%d,%d", &a1, &a2, &a3 );

    if ( a1 > a2 )
    {
        if ( a2 > a3 )
        {
            printf( "%d,%d,%d\n", a1, a2, a3 );
        }
        else
        {
            if ( a1 > a3 )
            {
                printf( "%d,%d,%d\n", a1, a3, a2 );
            }
            else
            {
                printf( "%d,%d,%d\n", a3, a1, a2 );
            }
        }
    }
    else
    {
        if ( a1 > a3 )
        {
            printf( "%d,%d,%d\n", a2, a1, a3 );
        }
        else
        {
            if ( a2 > a3 )
            {
                printf( "%d,%d,%d\n", a2, a3, a1 );
            }
            else
            {
                printf( "%d,%d,%d\n", a3, a2, a1 );
            }
        }
    }

    return 0;
}

Because every if statement now has a corresponding else statement, all cases are handled, including the case of all 3 numbers being identical.

This solution is also more efficient, because the maximum number of comparisons required is now only 3 instead of 12.

Alternatively, if you put all numbers into an array, you can sort the array and then print it. This will make things a lot easier when you have more than 3 numbers:

#include <stdio.h>
#include <stdlib.h>

int my_compare( const void *left, const void *right )
{
    int a = *(int*)left;
    int b = *(int*)right;

    if ( a < b )
        return 1;
    if ( a > b )
        return -1;

    return 0;
}

int main( void )
{
    //define array with many numbers
    int arr[] = { 14, 17, 19, 18, 17, 12, 15, 19 };
    const int arr_size = sizeof arr / sizeof *arr;

    //sort the array
    qsort( arr, arr_size, sizeof *arr, my_compare );

    //print the content of the sorted array
    for ( int i = 0; ; )
    {
        printf( "%d", arr[i] );
        if ( ++i == arr_size )
            break;
        printf( ", " );
    }

    return 0;
}

This program has the following output:

19, 19, 18, 17, 17, 15, 14, 12

Answer 2

Yes! You can't use the statement like this: if (a1>a2>a3), you need to write them like this:

if (a1>a2 && a2>a3)

And also one more thing you need to correct in this program that you need to check the conditions only once for one variable or also you can also take a look on the function by you can do it easily without writing that much much code within some lines you can solve it.

Answer 3

According to the C Standard (6.5.8 Relational operators)

6 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >= (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false. The result has type int.

And the operators are evaluated from left to right,

So if statements like that

if(a1>a2>a3)

are equivalent to

if( ( a1 > a2 ) > a3 )

And depending on whether a1 is greater than a2 or not you have either

if( ( 1 ) > a3 )

or

if( ( 0 ) > a3 )

Instead you need to include in the expression logical AND operator like

if( a1 > a2 && a1 > a3 )

But if you will do so the program can output nothing if at least two ages are equal each other.

Also in this call of scanf

scanf( "%d,%d,%d", &a1, &a2, &a3 );

it is better to remove commas between the conversion specifiers. Let the user will enter ages separated by spaces like for example

20 22 21

or

20
22
21

If you want to output the ages in the descending order you could write for example

#include <stdio.h>

int main( void )
{
    int a1, a2, a3;

    printf( "enter the age of ram,shyam and ajay: " );
    scanf( "%d %d %d", &a1, &a2, &a3 );

    if ( a1 < a2 )
    {
        int tmp = a1;
        a1 = a2;
        a2 = tmp;
    }

    if ( a2 < a3 )
    {
        int tmp = a2;
        a2 = a3;
        a3 = tmp;
    }
 
    if ( a1 < a2 )
    {
        int tmp = a1;
        a1 = a2;
        a2 = tmp;
    }

    printf( "%d, %d, %d\n", a1, a2, a3 );
}