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Solve LeetCode 3 Longest Substring Without Repeating Characters in C++ using the sliding window

Longest Substring Without Repeating Characters in C++ LeetCode 3 · sliding window · last index array Table of Contents Problem Statement Approach Algorithm C++ Program Input Sample Output Output Explanation Dry Run Flow of Execution Time Complexity Space Complexity Applications Key Points Interview Questions Frequently Asked Questions Conclusion Problem Statement 3. Longest Substring Without Repeating Characters Given a string s , find the length of the longest substring that contains no repeating characters. A substring is a continuous part of the string, so "pwke" is a subsequence of "pwwkew" but not a substring. Approach We use a sliding window . The window is the part of the string between start and end , and we always keep it free of repeated characters. An array lastIndex of size 128 remembers the most recent position of every ASCII ...

C++ Program to Reverse a String and Check Palindrome

C++ Program to Reverse a String and Check Palindrome

✅ C++ Program to Reverse a String and Check Whether It Is a Palindrome

#include <iostream>
#include <string.h>
using namespace std;

void rev(char str[]) {
    int start = 0, end = strlen(str) - 1;
    int temp;
    while (start < end) {
        temp = str[start];
        str[start] = str[end];
        str[end] = temp;
        start++;
        end--;
    }
}

void pal(char str[]) {
    int start = 0, end = strlen(str) - 1;
    while (start < end) {
        if (str[start] != str[end]) {
            cout << "No. String is not palindrome:\n";
            return;
        }
        start++;
        end--;
    }
    cout << "Yes. String is palindrome:\n";
}

int main() {
    char str[100];
    cout << "Enter the string:\n";
    cin.getline(str, 100);
    cout << "Before reverse:\n";
    cout << str;
    cout << "\nAfter reverse:\n";
    rev(str);
    cout << str << "\n";
    pal(str);
}
  

๐Ÿ“˜ Explanation:

This program uses two user-defined functions:

  • rev() — reverses the given string manually by swapping characters from start and end.
  • pal() — checks whether the string is palindrome by comparing characters from both ends.

The program uses cin.getline() to take a string input (including spaces) and strlen() from the string.h library to find string length.

๐Ÿงพ Sample Output:

Enter the string:
level
Before reverse:
level
After reverse:
level
Yes. String is palindrome:
  

๐Ÿ”‘ Keywords:

C++ palindrome program, reverse string in C++, string manipulation in C++, C++ functions example, palindrome check, character swapping, string length

๐Ÿ“Œ Hashtags:

#CPlusPlus #String #Palindrome #ReverseString #Programming #CPPBasics

๐Ÿ” Search Description:

Learn how to reverse a string and check if it is a palindrome using functions in C++. Includes full explanation, sample output, and dark-themed code example.

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