Given a string of words, we need to implement a function which reverses the order of the words in the string. For example, the string "*I work at Educative*" should become "*Educative at work I​*". 

# Algorithm

There are various methods used to reverse a given string; one of the most widely used algorithms is described below:

- First, reverse the letters in the individual words in the string. For example, the string "*I work at Educative*" should become "*I krow ta evitacudE*".  

- Then, reverse the whole string. So, "*I krow ta evitacudE*" becomes "*Educative at work I*".

The parameter(s) of the `reverse` function will depend on the algorithm in the respective language. In C++, the function takes a `start` and an `end` pointer to the string as parameters and reverses it by swapping the first and the last letters; ​it then swaps the second and the second to the ​last letter, and so on.

# Code

The algorithm above is implemented in the code snippet below:​

#include <iostream>
using namespace std;

// reverse function which takes the pointer to starting
// and ending character
void reverse(char* start, char* end)
{
  // loop over the word until the start meets end
  // in the middle
  for (start ; start < end ; start++)
  {
    // swap
    char temp;
    temp = *start;
    *start = *end;
    *end = temp;

    // move to the previous letter
    end--;
  }

}

int main() {
  
  string str = "I work at Educative";
  
  // pointers to starting characters of the string
  char* ind = &str[0];
  char* new_word = &str[0];

  // while there exists a character
  while(*ind)
  {
    // if a space is found, call reverse on the word
    // before the space
    if (*ind == ' ')
    {
      reverse(new_word, ind-1);
      
      // set the marking of a new word i.e right after
      // the space
      new_word = ind+1;
    }
    ind++;
  }

  // reverse the letters in the last word
  // the last word is not catered in the loop above
  reverse(new_word,--ind);

  // reverse the whole string
  reverse(&str[0], ind);
  

  cout << str;
  return 0;
}

# In Python, built-in functions like split
# and insert can be used without having to import any addition 
# libraries. The code is much simpler
# in Python.

# insert the words in the list from the end
def reverse(str):
  # split the string into list of words
  words = str.split(' ')
  rev_str =[] 
  for word in words: 
    rev_str.insert(0, word)
    
  return rev_str

str = "I work at Educative"
result = reverse(str);
print(" ".join(result)) 

Python

//  In Java, built-in functions like split
//  and string concatenation can be used without having to import 
// additional libraries
// The code is much simpler in Java.
class Reverse_String { 

	public static void main(String[] args) 
	{ 
		String str[] = "I work at Educative".split(" "); 
		
    String result = reverse(str);
		System.out.println(result); 
	}

  public static String reverse(String[] str)
  {
    String result = "";

		for (int i = str.length - 1; i >= 0; i--) { 
			result = result + str[i] + " "; 
		}
    
    return result;
  }
} 

Java

Reverse the order of words in a string

Reverse the order of words by first reversing the letters in each word and then reversing the entire string.