Reverse String

#include <bits/stdc++.h> // Includes necessary headers: <iostream>, <string>, <stack>
using namespace std;     // Use standard namespace

int main() {
    string str, answer; // Declare strings for original and reversed
    stack<char> s;      // Declare a stack to hold characters

    cout << "Enter the string : "; // Prompt user for input
    getline(cin, str);             // Read the entire line into 'str'

    // Step 1: Push all characters of the string onto the stack
    for(int i=0; i<str.length(); i++) {
        char ch = str[i]; // Get character at current index
        s.push(ch);       // Push character onto stack
    }

    // Step 2: Pop characters from stack and build reversed string
    while(! s.empty()) {     // Continue while stack is not empty
        char ch = s.top();   // Get top character
        answer.push_back(ch); // Append character to 'answer' string
        s.pop();             // Remove top character from stack
    }

    // Print results
    cout << "Original string : ";
    cout << str;
    cout << "\nReversed string : ";
    cout << answer;

    return 0; // Indicate successful execution
}

Core Idea

• LIFO Property: Stacks follow Last-In, First-Out. This means if you push characters “A”, “B”, “C”, when you pop, you get “C”, then “B”, then “A”. This naturally reverses the order.

Steps

1. Push All: Iterate through the original string and push each character onto the stack.
2. Pop All: Pop characters from the stack one by one and append them to a new string.
3. The new string will contain the reversed sequence.

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