Printing null character when input is odd character amount - c++

Question

I've been toying with this c program for a while, and I can't seem to figure out what I'm missing.
In the very bottom of my code, I have a function that replaces every other word with a "-".
My problem is that when I enter an odd numbered word, such as "Cat", "dog", "hamburger", it will place a "-" in what I think is the null character position, though I have not been able to debunk it.
Thank you for your help!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void replace(char w[]);
int main( )
{
char w[100], x[100], y[100];
int z = 0;
printf("Player 1, please enter the secret word: ");
fgets(x,100,stdin);
// system("clear");
while( strcmp(x,y) != 0 )
{
strcpy(w,x);
// printf("\nLength of String : %d", strlen(w)-1);
replace(w);
printf("Player 2, the word is %s\n",w);
printf("Player 2, please guess the word: ");
fgets(y,100,stdin);
z++;
if( strcmp(x,y) != 0 )
{
printf("Wrong. Try again.\n");
}
else
{
//system("clear");
printf("Correct!\n");
printf("It took you %d attempt(s).\n",z);
switch (z)
{
case 1 :
case 2 :
printf("A. Awesome work!");
{break;}
case 3 :
case 4 :
printf("B. Best, that was!");
{break;}
case 5 :
case 6 :
printf("C. Concentrate next time!");
{break;}
case 7 :
printf("D. Don't quit your day job.");
{break;}
default :
printf("F. Failure.");
{break;}
}
}
}
getch();
}
void replace(char w[])
{
int a;
a = 0;
while (w[a] != '\0')
{
if (a % 2 != 0)
{
w[a] = '-';
a++;
}
if (w[a] != '\0')
{
a++;
}
else
{
break;
}
}
}

Answer 1

From the fgets manual;
fgets() reads in at most one less than size characters from stream and stores them into the buffer pointed to by s. Reading stops after an EOF or a newline. If a newline is read, it is stored into the buffer. A terminating null byte (\0) is stored after the last character in the buffer.
The newline entered is what you're replacing.

Answer 2

You can implement like this...
int a;
int len;
a = 0;
len = strlen(w);
if(len%2 == 0)
len = len-1;
while (len!=a)
{
if (a % 2 != 0)
{
w[a] = '-';
a++;
}
if (w[a] != '\0')
{
a++;
}
else
{
break;
}
}

Answer 3

I think replacing fgets with just gets will work:
Try:
//fgets(x,100,stdin);
gets(x);
and
//fgets(y,100,stdin);
gets(y);
That will be enough I think.

Answer 4

The problem is caused by the additional '\n' character in the char array passed to the replace function.
For instance, when the input is "Cat", the passed char[] w contains {'C', 'a', 't', '\n', '\0'};
The additional '\n' also gets replaced with "-" character.
The following will solve this problem.
while (w[a] != '\0')
{
if (w[a] != '\0' && w[a] != '\n')
{
if (a % 2 != 0)
{
w[a] = '-';
}
a++;
}
else
{
break;
}
}

Answer 5

As a bit of an aside, can I suggest structuring your replace() code differently
void replace(char charw[])
{
int length=strlen(charw);
int i;
for (i=0;i<length;i++)
{
if (i%2==1) /*yes, i%2 would also work, but lets not get too clever*/
{charw[i]='-';}
}
}
This is far more readable. Breaking in the middle of a loop...not so much.