how to split words in a string in c? - c

Question

I need to build a program that receives up to 30 chars from the user, and then to play with it.
For example, I need to reverses the sentence and then print it, or to rotate it.
I have been trying to copy the words of the sentence one by one to a matrix of [30][31], but it does not working... any ideas?
I cannot use pointers...
thanks for the help :)
#include <stdio.h>
#include <string.h>
void main(){
int i=0,
j=0,
wrongData=0,
charCounter=0,
word=0,
letter=0;
char st[100],
arr[100]={0},
mat[30][31]={0};
printf("Please, enter your sentence >");
gets(st);
while(i<strlen(st)){
if('A'<=st[i] && st[i]<='Z'){
charCounter++;
arr[j] = st[i];
i++;
j++;
} else if(st[i]==' '){
arr[j] = ' ';
i++;
j++;
while(st[i] == ' '){
i++;
}
} else if(st[i]=='\0'){
arr[j] = '\0';
break;
} else {
puts("ERROR: Incorrect data, try again.");
wrongData=1;
break;
}
if(wrongData==0){
if(charCounter>30){
puts("ERROR: Incorrect data, try again.");
}
}
}
puts(st);
puts(arr);
if(arr[j]==' '){
word++;
}
while(arr[j]!=' ' && letter<32){
strcpy(mat[word],arr);
}
if(arr[j]=='\0'){
mat[word][letter]=arr[j];
}
puts(mat[word]);
}

Answer 1

Taking into account your comment
the problem is that i need to reverse the words not the letters... for
example: if the string is cats hates dogs, i need to get at the end
dogs hates cats
then I think you mean something as the following
#include <stdio.h>
#include <ctype.h>
#include <string.h>
char * reverse_words( char s[] )
{
for ( char *p = s, *q = s; *p; p = q )
{
while ( isspace( ( unsigned char )*p ) ) ++p;
q = p;
while ( *q && !isspace( ( unsigned char )*q ) ) ++q;
for ( size_t i = 0; i < ( q - p ) / 2; i++ )
{
char c = p[i];
p[i] = q[-i-1];
q[-i-1] = c;
}
}
for ( size_t i = 0, n = strlen( s ); i < n / 2; i++ )
{
char c = s[i];
s[i] = s[n-i-1];
s[n-i-1] = c;
}
return s;
}
int main( void )
{
char s[] = "cats hates dogs";
puts( s );
puts( reverse_words( s ) );
return 0;
}
The program output is
cats hates dogs
dogs hates cats

Answer 2

Here is another approach. The idea is to go through the string and record the index where each word starts and ends. Then the words can be printed in reverse order afterwards. (btw - it will also be easy to rotate the words).
#include<stdio.h>
#include <string.h>
int main() {
char st[100] = "here we go again";
int start[30] = { 0 };
int end[30] = { 0 };
int count = 0;
int len = strlen(st);
int i, j;
// Find start and end index of each word
start[0] = 0;
for(i = 0; i < len; ++i)
{
if (st[i] == ' ')
{
end[count] = i;
++count;
start[count] = i + 1;
}
}
end[count] = len;
// Print the words in reverse order
for(i=count; i >= 0; --i)
{
for (j = start[i]; j < end[i]; ++j)
{
printf("%c", st[j]);
}
printf(" ");
}
printf("\n");
return 0;
}
output:
again go we here

Answer 3

fix your approach like this:
#include <stdio.h>
//#include <string.h>
#define MAX_LEN 30
int main(void){
int i, j, n, word;
char st[100], arr[100], mat[MAX_LEN / 2][MAX_LEN + 1];
printf("Please, enter your sentence (up to %d chars and A-Z or space)\n>", MAX_LEN);fflush(stdout);
scanf("%99[^\n]%*c", st);
//validate and reduce of spaces
for(j = i = 0; st[i]; ++i){
if(i > MAX_LEN){
fputs("ERROR: Incorrect data, try again.\n", stderr);
return 1;
}
if('A'<=st[i] && st[i]<='Z'){
arr[j++] = st[i];
} else if(st[i]==' '){
arr[j++] = ' ';
while(st[++i] == ' ')//Skip a continuous space
;
--i;//one back for next loop
} else {
fputs("ERROR: Incorrect data, try again.\n", stderr);
return 1;
}
}
arr[j] = '\0';//st[i]=='\0' never become true in loop
#if DEBUG
puts(st);
puts(arr);
#endif
//split to word
for(word = j = i = 0; arr[i];){
while(arr[i] == ' ')
++i;//skip space
while(arr[i] != ' ' && arr[i] != '\0')
mat[word][j++] = arr[i++];
mat[word++][j] = '\0';
j = 0;
}
#if DEBUG
for(i = 0; i < word; ++i)
puts(mat[i]);
#endif
puts("reverse word");
for(i = 0; i < word; ++i){
if(i)
putchar(' ');
printf("%s", mat[word-1-i]);
}
puts("\nrotate word");
printf("Please, enter number of rotate\n>");fflush(stdout);
scanf("%d", &n);
for(i = 0; i < word; ++i){
if(i)
putchar(' ');
printf("%s", mat[(i+n)%word]);//rotate left
}
}