Infinite Loop when counting with an array [C] - c

Question

I've been trying to get back into C lately (for work related purposes) and I've been to a C refresher workshop. I can't seem to get my head around why an infinite loop occurs in this code.
I'm trying to code a program which returns the number of words within an array of characters. Any help would be greatly appreciated. Thanks!
// ArrayWords.c
#include <stdio.h>
#include <ctype.h>
#define LENGTH 50
int word_count(char []);
int main(void) {
char sentence[LENGTH];
int i;
printf("Enter a sentence with at most %d characters:\n", LENGTH);
for(i = 0; i < LENGTH; i++)
scanf("%s", &sentence[i]);
printf("Sentence = %s\n", sentence);
printf("Word count = %d\n", word_count(sentence));
return 0;
}
// Count the number of words in str
int word_count(char str[]) {
int i, word = 1;
for(i = 0; i < LENGTH; i++)
while(str[i] != '\0')
if((isspace(str[i])))
{
word++;
}
return word;
}

Answer 1

Your use of scanf isn't good.
word_count cause infinite loop because i isn't updated in the while loop.
fixed code:
// ArrayWords.c
#include <stdio.h>
#include <ctype.h>
#define LENGTH 50
int word_count(char []);
int main(void) {
char sentence[LENGTH];
printf("Enter a sentence with at most %d characters:\n", LENGTH);
fgets(sentence, sizeof(sentence), stdin);
printf("Sentence = %s\n", sentence);
printf("Word count = %d\n", word_count(sentence));
return 0;
}
// Count the number of words in str
int word_count(char str[]) {
int i = 0, word = 1;
while(str[i] != '\0') {
if((isspace(str[i])))
{
word++;
}
i++;
}
return word;
}

Answer 2

for(i = 0; i < LENGTH; i++)
scanf("%s", &sentence[i]);
Here you are reading a char one by one. so it should have %c, like scanf(" %c", &sentence[i]);
However, this wont be the right way to read the string. Since, it wont put the \0 in the end.
Since the string to be read will contain spaces, best way to do this would be fgets()
Your counting loop also has an error, either you can change it to one of the answers above or simply use a single for loop, like this
for(i = 0; i < LENGTH && str[i] != '\0'; i++)
if((isspace(str[i])))
{
word++;
}

Answer 3

In your code,i isn't actually in the loop.Besides,array contains the sentence with a \0 in the end,so if the length of the sentence is 50,the space must be 51 since at the end of it there is an \0,and scanf is not so good as it judges " "as a stop sign,gets can't stop until enter key which may cause overflow,so I use fgets.
#include <stdio.h>
#include <ctype.h>
#define LENGTH 50
int word_count(char []);
int main(void) {
char sentence[LENGTH+1];
printf("Enter a sentence with at most %d characters:\n", LENGTH);
fgets(sentence, sizeof(sentence), stdin);
printf("Sentence = %s\n", sentence);
printf("Word count = %d\n", word_count(sentence));
return 0;
}
// Count the number of words in str
int word_count(char str[]) {
char* p=str;
int word=0;
while(*p!='\0'){
if((isspace(*p))) word++;
p++;
}
return word;
}

Answer 4

You should read data from stdin, not scanf but fgets or gets!
Maybe fgets( sentence, LENGTH, stdin ) is good.
And in the function word_count you may replace while with if.

Answer 5

This part of the program
for(i = 0; i < LENGTH; i++)
scanf("%s", &sentence[i]);
does not make sense. It tries to enter LENGTH number of words in the loop.
I think you mean format specifier %c instead of %s
scanf("%c", &sentence[i]);
but even in this case this snippet of code is wrong because the user can enter either less than LENGTH characters or even greater than LENGTH characters and the character array sentence will not be zero-terminated..
It is better to use standard function fgets instead of scanf in this situation.
And function word_count is also wrong. For example if str would be zero-terminated nevertheless the outer for loop will try to count words outside the string. And the function in fact counts the number of spaces. It is not the same as the number of words. A string can contain adjasted spaces. This mistake is made by all others in their answers.:)
And inside the while loop variable i is not increased. So it is an infinite loop.
int word_count(char str[]) {
int i, word = 1;
for(i = 0; i < LENGTH; i++)
while(str[i] != '\0')
if((isspace(str[i])))
{
word++;
}
return word;
}
The program can look the following way
// ArrayWords.c
#include <stdio.h>
#include <ctype.h>
#define LENGTH 50
size_t word_count( const char[] );
int main( void )
{
char sentence[LENGTH];
printf( "Enter a sentence with at most %d characters: ", LENGTH );
fgets( sentence, LENGTH, stdin );
printf( "Sentence = \"%s\"\n", sentence );
printf( "Word count = %zu\n", word_count( sentence ) );
return 0;
}
// Count the number of words in str
size_t word_count( const char s[] )
{
size_t words = 0;
while ( *s != '\0' )
{
// skip white spaces
while ( isspace( ( unsigned char )*s ) ) ++s;
if ( *s != '\0' ) ++words;
// skip the word
while ( *s != '\0' && !isspace( ( unsigned char )*s ) ) ++s;
}
return words;
}
Its output might look like
Enter a sentence with at most 50 characters: Hello, Unholy Wish
Sentence = "Hello, Unholy Wish"
Word count = 3

Answer 6

It's not an infinite loop.
Your program is trying to read 50 (or LENGTH) words (and saving them on top of each other).
for(i = 0; i < LENGTH; i++)
scanf("%s", &sentence[i]);
Put first word starting at sentence[0];
put second word starting at sentence[1] overwriting characters from the first word;
...