﻿ C Program: Count the Lychrel numbers within a range

# C Exercises: Display and count the number of Lychrel numbers within a specific range.

## C Numbers: Exercise-9 with Solution

Write a program in C to display and count the number of Lychrel numbers within a specific range (from 1 to a specific upper limit).

Test Data
Input the upper limit: 1000

Sample Solution:

C Code:

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

bool palindrome ( unsigned long long int i );
unsigned long long int reverse ( unsigned long long int i );
bool lychrel ( unsigned long long int i );

int main ( void )
{
unsigned long long int i=0;
int count=0,ulmt;
printf("\n\n Display and count number of Lychrel numbers within a specific range: \n");
printf(" -------------------------------------------------------------------------\n");
printf(" Input the upper limit: ");
scanf("%d",&ulmt);
printf("\n The Lychrel numbers are:  \n");
for(i=1;i<ulmt;i++)
{
if(lychrel(i))
{
printf(" %llu ",i);
count++;
}
}
printf("\n The number of  Lychrel numbers are:  %d\n\n",count);
return 0;
}
bool lychrel ( unsigned long long int i )
{
int j; /*iteration counter*/
bool lychrel = true;
i = i + reverse ( i );

for ( j = 1; j <= 30 ; j++ )
{
if ( palindrome ( i ) )
{
lychrel = false;
break;
}
i = i + reverse ( i );
}

return lychrel;
}
unsigned long long int reverse ( unsigned long long int i )
{
unsigned long long int ret = 0;
while ( i != 0 )
{
ret *= 10;
ret += i % 10;
i /= 10;
}
return ret;
}

bool palindrome ( unsigned long long int i )
{
return ( i == reverse ( i ) );
}
```
```

Sample Output:

``` Input the upper limit: 1000

The Lychrel numbers are:
196  295  394  493  592  689  691  788  790  879  887  978  986
The number of  Lychrel numbers are:  13
```

Pictorial Presentation:

Flowchart:

C Programming Code Editor:

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﻿

## C Programming: Tips of the Day

Why does the smallest int, -2147483648, have type 'long'?

In C, -2147483648 is not an integer constant. 2147483648 is an integer constant, and - is just a unary operator applied to it, yielding a constant expression. The value of 2147483648 does not fit in an int (it's one too large, 2147483647 is typically the largest integer) and thus the integer constant has type long, which causes the problem you observe. If you want to mention the lower limit for an int, either use the macro INT_MIN from (the portable approach) or carefully avoid mentioning 2147483648:

```printf("PRINTF(d) \t: %d\n", -1 - 2147483647);
```

Ref : https://bit.ly/2S4P2he

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