📘 Day 4– Teacher's Day Challenge | Two Sum (Brute Force)

🗓️ Date: July 28, 2025
🔢 Problems Solved Today: 1
🎯 Focus Topic: Arrays, Brute Force

💻 Platform: Leetcode

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🔗 Table of Contents

• Problem 1 – Two Sum

• Daily Summary

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🧩 Problem 1 – Two Sum

📚 Difficulty: Easy
🧠 Concepts: Array Traversal, Brute Force

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📄 Problem Statement (Summary):
Find two indices in an array nums such that the elements at those indices sum up to a given target.
You must return the indices in any order. Each input has exactly one solution.

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Examples:

• Input: nums = [2,7,11,15], target = 9 → Output: [0,1]

• Input: nums = [3,2,4], target = 6 → Output: [1,2]

• Input: nums = [3,3], target = 6 → Output: [0,1]

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💡 Approach:

• Use nested loops to try every possible pair.

• Check if the sum of two elements equals the target.

• If so, return their indices immediately.

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🧪 Code (C++):

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        int sum = 0;
        vector<int> sum_arr;
        for (int i = 0; i < nums.size(); i++) {
            for (int j = i + 1; j < nums.size(); j++) {
                sum = nums[j] + nums[i];
                if (sum == target) {
                    sum_arr.push_back(i);
                    sum_arr.push_back(j);
                    return sum_arr;
                }
            }
        }
        return sum_arr;
    }
};

📸 Submission Screenshot:

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✅ Key Takeaways:

• Brute force is simple but inefficient with O(n²) time.

• Will explore optimized solutions using HashMaps (O(n)) later.

• Ensure you don’t reuse the same index twice.

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📈 Daily Summary

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🏷️ Tags:
#leetcode #43DaysChallenge #arrays #bruteforce #cpp #dsa #twosum #codingjourney