Program to Reverse words in a sentence (Java , C and Python)

The goal of this program is reverse words in a sentence
for eg : Original string: Neil Peart rocks YYZ
we need : YYZ rocks Peart Neil

To make life simple let us see two programs that use simple strategy of splitting the sentences based on delimiters in this case spaces ” ” and then append the splits to a buffer or a stack

The first strategy is to use a stack and implemented in Java

import java.util.*;
public class StringReverseWord 
{
        public static void main(String[] args) {
        String a = "Neil Peart rocks YYZ";
        Stack <String> stack = new Stack <String>();
        String[] temp;
	String delimiter = " ";
	// given string will be split by the argument delimiter provided. 
	temp = a.split(delimiter);
	// push substring to stack
	for(int i =0; i < temp.length ; i++)
	{
            stack.push(temp[i]);
        }
        System.out.println("\nOriginal string: " + a);
        System.out.print("Reverse word string: ");
        while(!stack.empty()) {
            System.out.print(stack.pop());
            System.out.print(" ");
        }
        System.out.println("\n");
    }
}

OUTPUT:
laptop:~/code$ java StringReverseWord

Original string: Neil Peart rocks YYZ
Reverse word string: YYZ rocks Peart Neil

Below is a Java implementation using an additional buffer with same strategy of splitting based on a space delimiter

import java.io.*;
public class ReverseWords
{	
    public static  void main(String[] args) {
    String s = "Neil Peart rocks YYZ";
    String[] str =s.split(" ");
    StringBuffer buffer = new StringBuffer();
    for(int i=str.length-1;i>=0;i--)
    {
        buffer.append(str[i]);
        buffer.append(" ");
    }
    System.out.println("\nOriginal string: " + s);
    System.out.println("Reverse word string:"+buffer.toString());
    }
}

OUTPUT:
laptop:~/code$ java ReverseWords
Original string: Neil Peart rocks YYZ
Reverse word string:YYZ rocks Peart Neil

The Below program is implemented in C and uses a strategy of reversing individual words initially and then reversing this resultant string.

#include<stdio.h>
/* function to reverse a string */
void reverse(char *start, char *end);
 
/*Function to reverse words*/
void reversewords(char *s)
{
  char *word = s;
  char *temp = s; 
 
  /*start reversing the individual words*/
  while( *temp ) 
  {
    temp++;
    if (*temp == '\0')
    {
      reverse(word, temp-1);
    }
    else if(*temp == ' ')
    {
      reverse(word, temp-1);
      word = temp+1;
    }
  }  
  reverse(s, temp-1);/*Reverse the resultant string from beginning to end including spaces*/
}
/*Function to reverse a string this is similar to earlier blog post to reverse a string */
void reverse(char *start, char *end)
{
  char temp;
  while (start < end)
  {
    temp = *start;
    *start++ = *end;
    *end-- = temp;
  }
}
int main()
{
  char s[] = "Neil Peart rocks YYZ";
  char *temp = s;
  printf("Original string: %s\n",s);
  reversewords(s);
  printf("Reverse word string: %s\n", s);
  return 0;
}

OUTPUT:
laptop:~/code$ ./a.out
Original string: Neil Peart rocks YYZ
Reverse word string: YYZ rocks Peart Neil

For python coders

laptop:~/code$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> string = "Neil Peart rocks YYZ"
>>> " ".join(string.split()[::-1])
'YYZ rocks Peart Neil'

The code in this article is to illustrate the approach taken to solve this usual problem and does not cover all test cases. Keep posting your fail proof versions in the comments.

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