Reverse the Sentence using Stack

Given a string str consisting of a sentence, the task is to reverse the entire sentence word by word.

Examples:

Input: str = “geeks for geeks”
Output: geeks for geeks

Input: str = “data structures and algorithms”
Output: algorithms and structures data

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: An approach without using stack is discussed here. This problem can also be solved using stack by following the below steps:

Create an empty stack.
Tokenize the input string into words using spaces as separator with the help of strtok()
Push the words into the stack.
Pop the words from the stack until the stack is not empty which will be in reverse order.

Below is the implementation of the above approach:

C++

// C++ implementation of the approach 
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to reverse the words 
// of the given sentence 
void reverse(char k[]) 
{ 
  
    // Create an empty character array stack 
    stack<char*> s; 
    char* token = strtok(k, " "); 
  
    // Push words into the stack 
    while (token != NULL) { 
        s.push(token); 
        token = strtok(NULL, " "); 
    } 
  
    while (!s.empty()) { 
  
        // Get the words in reverse order 
        cout << s.top() << " "; 
        s.pop(); 
    } 
} 
  
// Driver code 
int main() 
{ 
    char k[] = "geeks for geeks"; 
    reverse(k); 
  
    return 0; 
} 

Java

// Java implementation of the approach 
import java.util.Arrays; 
import java.util.Stack; 
  
class GFG  
{ 
      
// Function to reverse the words 
// of the given sentence 
static void reverse(String k) 
{ 
  
    // Create an empty character array stack 
    Stack<String> s = new Stack<>(); 
    String[] token = k.split(" "); 
      
    // Push words into the stack 
    for(int i = 0; i < token.length; i++) 
    { 
        s.push(token[i]); 
    } 
  
    while (!s.empty())  
    { 
  
        // Get the words in reverse order 
        System.out.print(s.peek() + " "); 
        s.pop(); 
    } 
} 
  
// Driver code 
public static void main(String[] args)  
{ 
    String k = "geeks for geeks"; 
    reverse(k); 
} 
} 
  
// This code is contributed by Rajput-Ji 

Python3

# Python3 implementation of the approach  
  
# Function to reverse the words  
# of the given sentence  
def reverse(k): 
    # Create an empty character array stack  
    s = []  
    token = k.split() 
      
    # Push words into the stack  
    for word in token : 
        s.append(word); 
          
    while (len(s)) : 
        # Get the words in reverse order  
        print(s.pop(),end= " ");  
      
  
# Driver code  
if __name__ == "__main__" :  
  
    k = "geeks for geeks";  
    reverse(k);  
      
# This code is contributed by AnkitRai01 

C#

// C# implementation of the approach 
using System; 
using System.Collections.Generic; 
  
class GFG  
{ 
      
// Function to reverse the words 
// of the given sentence 
static void reverse(String k) 
{ 
  
    // Create an empty character array stack 
    Stack<String> s = new Stack<String>(); 
    String[] token = k.Split(' '); 
      
    // Push words into the stack 
    for(int i = 0; i < token.Length; i++) 
    { 
        s.Push(token[i]); 
    } 
  
    while (s.Count != 0)  
    { 
  
        // Get the words in reverse order 
        Console.Write(s.Peek() + " "); 
        s.Pop(); 
    } 
} 
  
// Driver code 
public static void Main(String[] args)  
{ 
    String k = "geeks for geeks"; 
    reverse(k); 
} 
} 
  
// This code is contributed by PrinciRaj1992 

Output:

geeks for geeks

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

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