📘 Day 12 – Teacher’s Day Challenge | Petya and Strings

🗓️ Date: August 05, 2025
🧩 Platform: Codeforces
🔢 Problems Solved Today: 1
🎯 Focus Topic: String Comparison, Lexicographic Order, Case Insensitivity

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🔗 Table of Contents

• Problem 1 – Petya and Strings

• Daily Summary

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🧩 Problem 1 – Petya and Strings

📚 Difficulty: Easy
🧠 Concepts: String Transformation, Case-Insensitive Comparison, Lexicographical Order

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📄 Problem Statement (Summary):
Petya receives two strings of equal length containing uppercase and lowercase letters. He wants to compare them lexicographically, ignoring case sensitivity.

Your task is to:

• Convert both strings to lowercase.

• Compare them:

  • Output -1 if the first string is lexicographically smaller.

  • Output 1 if the first is greater.

  • Output 0 if they are equal.

Examples:
Input:
aaaa
aaaA
Output: 0

Input:
abs
Abz
Output: -1

Input:
abcdefg
AbCdEfF
Output: 1

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💡 Approach:

• Read both strings.

• Use transform() to convert both to lowercase.

• Compare character by character:

  • If any character in str1 < str2 → print -1

  • If any character in str1 > str2 → print 1

  • If none differ → print 0

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🧪 Code (C++):

#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
    string str1, str2;
    cin >> str1 >> str2;
    transform(str1.begin(), str1.end(), str1.begin(), ::tolower);
    transform(str2.begin(), str2.end(), str2.begin(), ::tolower);
    for (int i = 0; i < str1.length(); i++)
    {
        if (str1[i] < str2[i])
        {
            cout << -1;
            return 0;
        }
        else if (str1[i] > str2[i])
        {
            cout << 1;
            return 0;
        }
    }
    cout << 0;
    return 0;
}

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📸 Submission Screenshot:

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✅ Key Takeaways:

• transform() with ::tolower is perfect for case-insensitive tasks.

• Lexicographical comparison is simply done with direct character comparison.

• Always check equality only after confirming no differences were found.

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📈 Daily Summary

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🏷️ Tags:
#codeforces #strings #tolower #lexicographic #cpp #dsa #43DaysChallenge