Reverse words in C Language - c

Question

I'm trying to reverse the letters for words in a sentence. I am also trying to store these words in a new char array. At the moment I getting a runtime error, which for all my tweaking I can not solve. My approach is to create a new char array the same length as the sentence. Then loop through the sentence until I reach a ' ' character. Then loop backwards and add these characters to a word. Then add the word to the new Sentence. Any help would be much appreciated.
int main(void) {
char sentence [] = "this is a sentence";
char *newSentence = malloc(strlen(sentence)+1);
int i,j,start;
start = 0;
for(i = 0; i <= strlen(sentence); i++)
{
if(sentence[i] == ' ')
{
char *word = malloc((i - start)+1);
for(j = sentence[i]; j >= start; j--)
{
word[j] = sentence[j];
}
strcat(newSentence,word);
start =sentence[i +1];
}
}
printf("%s",newSentence);
return 0;
}

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char sentence [] = "this is a sentence";
char *newSentence;
int i,j,start, len;
start = 0;
len = strlen(sentence);
newSentence = malloc(len+1);
*newSentence = '\0';
for(i = 0; i <= len; i++)
{
if(sentence[i] == ' ' || sentence[i] == '\0')
{
char *word = malloc((i - start)+1);
int c = 0;
for(j = i - 1; j >= start; j--)
{
word[c++] = sentence[j];
}
word[c]='\0';
strcat(newSentence,word);
if(sentence[i] == ' ')
strcat(newSentence," ");
start = i + 1;
free(word);
}
}
printf("%s",newSentence);
return 0;
}

Answer 2

Logically, here:
j = sentence[i]
start =sentence[i +1];
start and j are index positions in the char array, you are trying to assign a char to them, which screws everything up.
should be:
j= i;
start = i +1;
if your algorithm is right.

Answer 3

Yet another variant of the same...
int main(int argc, const char *argv[])
{
char sentence [] = "this is a sentence";
size_t len = strlen(sentence);
char *newSentence = malloc(len + 1);
char *ptr_src = sentence;
char *ptr_dst = newSentence;
while(ptr_src)
{
char *next, *t;
next = strchr(ptr_src, ' '); // find next space
if (!next) next = sentence + len; // if not found, next = EOL
for (t = next; t > ptr_src;)
{
*ptr_dst++ = *--t;
}
if (*next)
{
*ptr_dst++ = *next++;
ptr_src = next;
}
else
{
*ptr_dst = 0;
break;
}
}
printf("[%s]",newSentence);
return 0;
}

Answer 4

Your program had few bugs. Which I've tried to remove in this program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char sentence [] = "this is a sentence";
char *newSentence = (char *)malloc(strlen(sentence)+1);
int i,j,start, k;
start = 0;
for(i = 0;; i++)
{
if(sentence[i] == ' ' || sentence[i] == '\0') //sentence[i] == '\0' for the last word.
{
char *word = (char *) malloc((i - start)+1);
for(j = i-1, k = 0; j >= start; j--, k++)
{
word[k] = sentence[j];
}
word[k++] = ' '; //space after each word
word[k] = '\0';
strcat(newSentence,word);
start = i+1;
}
if (sentence[i] == '\0')
break;
}
printf("%s\n",newSentence);
return 0;
}
Check live at http://ideone.com/Z9ogGk

Answer 5

strcat(newSentence,word);
newSentence has to be a string. And a string is a contiguous sequence of characters terminated by and including the first null character
EDIT: this answer has been downvoted 4 times for what is written above. If you think it is incorrect, please explain. Otherwise please remove your downvote.