Reverse the words in a string without changing their order?

Question

Say you are given "Hello World"
Output should be "olleH dlroW"

Comments

Example string "Hello World"
Start reading original string character by character and push it in a stack of characters and also mark start of the current word(start =0 for the first word). If reached space start popping characters from stack and copy them the start point marked, and update start(start = 6) with loop_counter + 1(loop_counter will be 5 at this time as space is at index 5).

Comments invited

Answer 1

Python code

import re
text = "This is a text for testing !"

for m in re.finditer(r"\w+", text):
     text = text[0:m.start()] + text[m.start():m.end()][::-1] +text[m.end():]

print text

Answer 2

See this simple program where I am managing the boundary and just reversing the characters within the boundary and it works

#include <stdio.h>

void reverse(char *begin, char *end)
{
  char temp;
  while (begin < end)
  {
    temp = *begin;
    *begin++ = *end;
    *end-- = temp;
  }
}

void reverseWords(char *s)
{
  char *word_begin = s;
  char *temp = s;

  while( *temp )
  {
    temp++;
    if (*temp == '\0')
    {
      return;
    }
    else if(*temp == ' ')
    {
      reverse(word_begin, temp-1);
      word_begin = temp+1;
    }
  }
}

main()
{
        char words[] = "this is a test";
        reverseWords(words);
        printf("%s\n", words);
}

Answer 3

Try this its working fine in C using recursion

#include <stdio.h>

void reverse();

void main() {      
        printf("Please enter a sentence: ");
        reverse();
        getch();
}    

void reverse() {    
        char c;
        scanf("%c",&c);
        if(c != '\n') {      
            reverse();
            printf("%c",c);
        }   
}