Question

How to Implement the rot13 algorithm in C

Answer 1

#include <stdio.h> 

#define ROT 13

int main(void)
{   
int ch, chrot;

	while ((ch=getchar())!=EOF) // Enter + Ctrl-C to exit
	{
		if (ch >='A' && ch <='Z')
		{
			if ((chrot = ch + ROT) <= 'Z')
				putchar(chrot);
			else
			{
				chrot = ch - ROT;
				putchar(chrot);
			}
		}
		else if (ch >='a' && ch <='z')
		{
			 if ((chrot= ch + ROT) <= 'z')
				putchar(chrot);
			 else
			 {
				chrot = ch - ROT;
				putchar(chrot);
			 }
		}
		else
			putchar(ch);
	}

    return 0;
}


 
/*
run:
   
abcdefg
nopqrst

*/

 

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