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:
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C Programming: Tips of the Day
Static variable inside of a function in C
The scope of variable is where the variable name can be seen. Here, x is visible only inside function foo().
The lifetime of a variable is the period over which it exists. If x were defined without the keyword static, the lifetime would be from the entry into foo() to the return from foo(); so it would be re-initialized to 5 on every call.
The keyword static acts to extend the lifetime of a variable to the lifetime of the programme; e.g. initialization occurs once and once only and then the variable retains its value - whatever it has come to be - over all future calls to foo().
Ref : https://bit.ly/3fOq7XP
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