Given a string str, the task is to reverse the string by considering each word of the string, **str **as a single unit.

Examples:

Input:_ str = “geeks quiz practice code”_

Output:_ code practice quiz geeks _

_Explanation: _

_The words in the given string are [“geeks”, “quiz”, “practice”, “code”]. _

Therefore, after reversing the order of the words, the required output is“code practice quiz geeks”.

Input: str = “getting good at coding needs a lot of practice”

Output: practice of lot a needs coding at good getting

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

In-place Reversal Approach: Refer to the article Reverse words in a given string for the in-place reversal of words followed by reversal of the entire string.

Time Complexity:_ O(N) _

Auxiliary Space:_ O(1)_

Stack**-based Approach: **In this article, the approach to solve the problem using Stack is going to be discussed. The idea here is to push all the words of str into the Stack and then print all the elements of the Stack. Follow the steps below to solve the problem:

1. Create a Stack to store each word of the string str.
2. Iterate over string str, and separate each word of** str** by a space delimiter.
3. Push all the words of **str **into the stack.
4. Print all the elements of the stack one by one.

Below is the implementation of the above approach:

C++

// C++ Program to implememnt

// the above approach

#include <bits/stdc++.h>

**using** **namespace** std;

// Function to reverse the words

// of a given string

**void** printRev(string str)

{

// Stack to store each

// word of the string

stack<string> st;

// Store the whole string

// in string stream

stringstream ss(str);

string temp;

**while** (getline(ss, temp, ' '``)) {

// Push each word of the

// string into the stack

st.push(temp);

}

// Print the string in reverse

// order of the words

**while** (!st.empty()) {

cout << st.top() << " "``;

st.pop();

}

}

// Driver Code

**int** main()

{

string str;

str = "geeks quiz practice code"``;

printRev(str);

**return** 0;

}

Python3

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## Python3 program to implememnt

## the above approach

## Function to reverse the words

## of a given strring

**def** printRev(strr):

## Stack to store each

## word of the strring

strr **=** strr.split(``" "``)

st **=** []

## Store the whole strring

## in strream

**for** i **in** strr:

## Push each word of the

## into the stack

st.append(i)

## Print the in reverse

## order of the words

**while** len``(st) > 0``:

**print**``(st[``**-**``1``], end **=** " "``)

**del** st[``**-**``1``]

## Driver Code

**if** __name__ **==** '__main__'``:

strr **=** "geeks quiz practice code"

printRev(strr)

## This code is contributed by mohit kumar 29

Output:

code practice quiz geeks

**Time Complexity: **O(N), where N denotes the length of the string.

Auxiliary Space: O(N)

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#stack #strings #reverse #substring