Implementing Reverse Words in a String using a Stack

Reversing the order of words in a string is a common problem in string manipulation. This task can be easily and efficiently accomplished using a stack data structure, a versatile tool for maintaining a history of elements. In this article, we will guide you through the process of reversing the words in a given string while considering edge cases related to spaces and handling each word one by one with the help of a stack.

Why Use a Stack?

A stack is a last-in-first-out (LIFO) data structure, making it an excellent choice for managing sequences of elements such as words in a string. By using a stack, we can temporarily store individual words and then pop them in reverse order to achieve the desired reversed word sequence. This approach ensures that the words are processed and stored correctly, and the final reversed string is constructed efficiently.

Algorithm Steps

The algorithm for reversing words in a string using a stack involves the following steps:

Initialize: Create an empty stack to store the words. Traverse the String: Iterate through the string character by character. Handle Spaces: If a space character is encountered, continue to the next character without processing the word. Process Words: When a non-space character is encountered, start collecting characters to form a word. If a space is encountered while forming a word, push the formed word onto the stack, and start a new word. Finalize: After the loop completes, pop words from the stack in reverse order to form the final reversed string.

Code Implementation

The following code demonstrates the implementation of the algorithm described above:

string reverseWords(string s) {
    stack st;
    for(int i  0; i  s.length(); i  ) {
        string word  "";
        if (s[i]  ' ') {
            continue;
        }
        while (i  s.length()  s[i] ! ' ')
        {
            word   s[i];
            i  ;
        }
        st.push(word);
    }
    string ans  "";
    while (!st.empty()) {
        ans   ();
        st.pop();
        if (!st.empty()) {
            ans   ' ';
        }
    }
    return ans;
}

Explanation of the Code

Initialize Stack: A stack st is created to temporarily store words. Traverse the String: The loop iterates through each character s[i] of the string s. Handle Spaces: If the character is a space, the loop continues without processing the current word. Process Words: When a non-space character is encountered, initialize word to an empty string and collect subsequent characters until a space is found or the end of the string is reached. Each formed word is then pushed onto the stack. Build the Final String: After the loop completes, the stack is popped to form the final reversed string. Each word is popped from the stack and appended to the result string ans. A space is added between words unless the stack is empty.

Conclusion

Using a stack to reverse the words in a string is both efficient and straightforward. This method ensures that the words are processed and stored correctly, and the final reversed string is assembled accurately. By following the steps outlined in this article, you can easily implement this technique in your own projects. Whether you are working on a larger project or just looking to solve string manipulation problems, mastering this technique will prove to be a valuable skill.

Related Keywords

Reverse words String manipulation Stack data structure