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