C :

/*
 * =====================================================================================
 *
 *       Filename:  902-3.c
 *
 *    Description:  ihahah
 *
 *        Version:  1.0
 *        Created:  2013/9/3 0:32:01
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  mdk-vim.cpp-c (mdk), mengdaikun@gmail.com
 *        Company:  cjluacm-vim-mdk
 *
 * =====================================================================================
 */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

char s[1001];
 
void reverse(int begin,int end)
{
    while(begin<end)
    {
        char temp=s[begin];
        s[begin]=s[end];
        s[end]=temp;
        ++begin;
        --end;
    }
}
 
int main()
{
    //freopen("a.in","r",stdin);
    
    while(gets(s))
    {
        int len=strlen(s),begin=0;
        
        reverse(0,len-1);
        
        int i;

        for(i=0;i<len;i++)
        {
            if(s[i]!=' ')
            {
                if(i>0&&s[i-1]==' ')
                    begin=i;
                else if(i<len-1&&s[i+1]==' ' || i==len-1)
                    reverse(begin,i);
            }
        }
        
        printf("%s\n",s);
    }
    return 0;
}
 

C++ :

#include <stdio.h>
///////////////////////////////////////////////////////////////////////
// Reverse a string between two pointers
// Input: pBegin - the begin pointer in a string
//        pEnd   - the end pointer in a string
///////////////////////////////////////////////////////////////////////
void Reverse(char *pBegin, char *pEnd)
{
      if(pBegin == NULL || pEnd == NULL)
            return;

      while(pBegin < pEnd)
      {
            char temp = *pBegin;
            *pBegin = *pEnd;
            *pEnd = temp;

            pBegin ++, pEnd --;
      }
}
///////////////////////////////////////////////////////////////////////
// Reverse the word order in a sentence, but maintain the character
// order inside a word
// Input: pData - the sentence to be reversed
///////////////////////////////////////////////////////////////////////
char* ReverseSentence(char *pData)
{
      if(pData == NULL)
            return NULL;

      char *pBegin = pData;
      char *pEnd = pData;

      while(*pEnd != '\0')
            pEnd ++;
      pEnd--;

      // Reverse the whole sentence
      Reverse(pBegin, pEnd);

      // Reverse every word in the sentence
      pBegin = pEnd = pData;
      while(*pBegin != '\0')
      {
            if(*pBegin == ' ')
            {
                  pBegin ++;
                  pEnd ++;
                  continue;
            }
            // A word is between with pBegin and pEnd, reverse it
            else if(*pEnd == ' ' || *pEnd == '\0')
            {
                  Reverse(pBegin, --pEnd);
                  pBegin = ++pEnd;
            }
            else
            {
                  pEnd ++;
            }
      }

      return pData;
}
int main()
{
	char s[9999];
	gets(s);
	while(s[0]!=0)
	{
		printf("%s\n",ReverseSentence(s));
		s[0]=0;
		gets(s);
	}
	return 0;
} 

Pascal :

program p2152;
var st,s:ansistring;
    i,j,k,n:longint;
begin
  while not eof do
   begin
     s:='';
     readln(st);
     k:=pos(' ',st);
     while k<>0 do
      begin
        s:=' '+copy(st,1,k-1)+s;
        delete(st,1,k);
        k:=pos(' ',st);
      end;
     if length(st)>0 then
      s:=st+s;
     writeln(s);
   end;
end.

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner cin = new Scanner(System.in);
		while(cin.hasNext())
		{
			String str = cin.nextLine();
			revString(str);
		}
	}
	
	public static String revString(String str)
	{
		StringBuilder builder = new StringBuilder();
		builder.append("begin ");
		builder.append(str);
		builder.append(" end");
		String []subStrings = builder.toString().split(" ");
		for(int i= subStrings.length -2 ;i>=2;i-- ){
			System.out.print(subStrings[i]+" ");
		}
		System.out.println(subStrings[1]);
		return null;
	}

}