void reverseString(char string[],char *start, char* end)
{

    char tmp; //temporary variable to swap values
    int count = 0;
    while(start<end)
    {
        if(*start==' ')
        {
            printf("found space count %d n",count);
            reverseString(string,start-count,start);
        }
        tmp = *start;
        *start = *end;
        *end = tmp;
        *start++;
        *end--;
        count++;
    }

    printf(" string %s n", string);
}

int main()
{
    char string[] = "reverse a string word by word";
    char *start =string;
    char *end =start+ strlen(string) -1;
    reverseString(string,start,end);
    return 0;
}

#include <stdio.h>
#include <string.h>

void stringrev(char *);
void reverseWords(char *);
void reverseString(char* , int);

int main()
{

    char string[] = "reverse a string word by word";
    reverseWords(string);
    printf("nWord-Wise Reversed String : %sn",string);
    stringrev(string);
    return 0;

}

void reverseWords(char * str)
{
    int i = 0, j = 0;
    reverseString( str, strlen(str) );
    while( 1 ) // Loop forever
    {
        if( *(str+j) == ' ' || *(str+j) == '') // Found a word or reached the end of sentence
        {
            reverseString( str+i, j-i );
            i = j+1;
        }
        if( *(str+j) == '')
        {
            break;
        }
        j++;
    }
}

void reverseString(char* str, int len)
{
    int i, j;
    char temp;
    i=j=temp=0;

    j=len-1;
    for (i=0; i<j; i++, j--)
    {
        temp=str[i];
        str[i]=str[j];
        str[j]=temp;
    }
}

void stringrev(char *str)
{
    int i=-1,j=0;
    char rev[50];

    while(str[i++]!='');

        while(i>=0)
         rev[j++] = str[i--];

    rev[j]='';

    printf("nComplete reverse of the string is : %sn",rev);
}

void reverse_string_word(char *data)
{
    char *saveptr;
    char *word;
    char *tmp = malloc(strlen(data) + 1);
    char *tmp2 = malloc(strlen(data) + 1);

    *tmp = 0;
    *tmp2 = 0;

    word = strtok_r(data, " ", &saveptr);
    if (word)
    {
        strcpy(tmp, word);
    }
    while (word)
    {
       word = strtok_r(NULL, " ", &saveptr);
       if (word)
       {
          sprintf(tmp2, "%s %s", word, tmp);
          strcpy(tmp, tmp2);
       }
    }
    strcpy(data, tmp);
    free(tmp);
    free(tmp2);
}

"one two three four" is returned as "four three two one"

private void reverseWordsNoStackNoScanner(String str) {
        System.out.println("reverseWordsNoStackNoScanner "+str);

        String[] buff = new String[str.length()];
        int end=str.length()-1;
        int j=end;
        int start=0;
        int ptr=0;
        for (int i=str.length()-1;i>=0;i--){
            boolean writeBuff=false;
            if (str.charAt(i)!=' ') { // have we backed up to a blank?
                j--; //no
            } else { //yes! write out this word
                writeBuff=true;
            }
            if (i==0) writeBuff=true; //are we done (position 0)?

            if (writeBuff) { //time to write a word?
                //we've hit a delimiter (or we're done)
                ptr=j;  //pointing at a blank or the beginning
                ptr++;  //bump past the blank or the beginning
                while(ptr<=end){ //write the word from beginning to finish
                    buff[start++]=String.valueOf(str.charAt(ptr++));
                }
                //don't write a blank when we are on the last word (past the end)
                if (i>0)buff[start++]=" ";
                j--;
                //set pointers for next iteration
                end=j; //back up end ptr to new 'end' - to parse the next word
            }
        }
            //print out our reversed word string
        for (String s: buff) {
            System.out.print(s);
        }
    }