📘Day 13 – Teacher’s Day Challenge | Helpful Maths

🗓️ Date: August 06, 2025
🧩 Platform: Codeforces
🔢 Problems Solved Today: 1
🎯 Focus Topic: Strings, Sorting

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🔗 Table of Contents

• Problem 1 – Helpful Maths

• Daily Summary

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🧩 Problem 1 – Helpful Maths

📚 Difficulty: Easy
🧠 Concepts: String Manipulation, Sorting

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📄 Problem Statement (Summary):
Xenia, a beginner at math, wants to calculate a sum but only if the numbers are in non-decreasing order.
You are given a string containing only digits 1, 2, 3 and '+' signs (e.g., "3+2+1"). Rearrange it so that the numbers appear in increasing order (e.g., "1+2+3"), and print the new string.

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🔢 Input Format:
A single string s containing digits 1, 2, 3 and '+'.

🧾 Output Format:
Print the reordered sum where digits appear in non-decreasing order, separated by '+'.

🔍 Example 1:
Input:
3+2+1
Output:
1+2+3

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🔍 Example 2:
Input:
1+1+3+1+3
Output:
1+1+1+3+3

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💡 Approach:

• Read the input string.

• Extract only the digits (1, 2, 3) from it.

• Sort the digits.

• Reconstruct the output string by joining digits with '+'.

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🧪 Code (C++):

#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main() {
    string s, str;
    cin >> s;

    // Extract only digits from the input
    for (char c : s) {
        if (c == '1' || c == '2' || c == '3') {
            str += c;
        }
    }

    // Sort the extracted digits
    sort(str.begin(), str.end());

    // Output in required format
    for (int i = 0; i < str.length() - 1; i++) {
        cout << str[i] << "+";
    }
    cout << str[str.length() - 1];

    return 0;
}

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📸 Submission Screenshot:

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✅ Key Takeaways:

• Convert the input into useful data by filtering characters.

• Sort the result to follow non-decreasing order.

• Reconstruct formatted output using loops and conditionals.

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📈 Daily Summary

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🏷️ Tags:
#codeforces #string #sorting #beginner #cpp #dsa #43DaysChallenge