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
In-place Reversal Approach: Refer to the article Reverse words in a given string for the in-place reversal of words followed by a reversal of the entire string.
Time Complexity: O(N)
Auxiliary Space: O(1)
Stack-based Approach: In this article, the approach to solving 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:
- Create a Stack to store each word of the string str.
- Iterate over string str, and separate each word of str by a space delimiter.
- Push all the words of str into the stack.
- 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; } |
Java
// Java Program to implememnt // the above approach import java.util.*; class GFG{ // Function to reverse the words // of a given String static void printRev(String str) { // Stack to store each // word of the String Stack<String> st = new Stack<String>(); // Store the whole String // in String stream String[] ss = str.split( " " ); for (String temp : ss) { // Push each word of the // String into the stack st.add(temp); } // Print the String in reverse // order of the words while (!st.isEmpty()) { System.out.print(st.peek() + " " ); st.pop(); } } // Driver Code public static void main(String[] args) { String str; str = "geeks quiz practice code" ; printRev(str); } } // This code is contributed by Rajput-Ji |
Python3
# 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 |
C#
// C# program to implememnt // the above approach using System; using System.Collections; class GFG{ // Function to reverse the words // of a given String static void printRev( string str) { // Stack to store each // word of the String Stack st = new Stack(); String[] sepearator = { " " }; // Store the whole String // in String stream string [] ss = str.Split(sepearator, int .MaxValue, StringSplitOptions.RemoveEmptyEntries); foreach ( string temp in ss) { // Push each word of the // String into the stack st.Push(temp); } // Print the String in reverse // order of the words while (st.Count > 0) { Console.Write(st.Peek() + " " ); st.Pop(); } } // Driver Code public static void Main( string [] args) { string str; str = "geeks quiz practice code" ; printRev(str); } } // This code is contributed by rutvik_56 |
code practice quiz geeks
Time Complexity: O(N), where N denotes the length of the string.
Auxiliary Space: O(N)
Method #2 :Using built in python functions
- As all the words in a sentence are separated by spaces.
- We have to split the sentence by spaces using split().
- We split all the words by spaces and store them in a list.
- Reverse this list and print it
Python3
# Python3 program to implememnt # the above approach # Function to reverse the words # of a given strring def printRev(string): # split by space and converting # string to list lis = list (string.split()) # reverse the list lis.reverse() # printing the list print ( * lis) # Driver Code if __name__ = = '__main__' : strr = "geeks quiz practice code" printRev(strr) # This code is contributed by vikkycirus |
code practice quiz geeks
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.