✅ Topics for Day 6 DSA with Java

Focus: Two Pointer Technique

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🔁 1. Learn & Implement Two Pointer Technique

• Understand how the two-pointer technique works on sorted arrays.

• Implement the following problems:

// Java Example: Two Sum (Sorted Array)
public int[] twoSum(int[] numbers, int target) {
    int left = 0, right = numbers.length - 1;
    while (left < right) {
        int sum = numbers[left] + numbers[right];
        if (sum == target) {
            return new int[] { left + 1, right + 1 }; // 1-indexed
        } else if (sum < target) {
            left++;
        } else {
            right--;
        }
    }
    return new int[] {}; // no solution
}

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🧠 2. Solve 2 LeetCode Problems Using Two Pointers

1. LeetCode 167. Two Sum II – Input Array Is Sorted

2. LeetCode 283. Move Zeroes

   • Optimize with minimal swaps using the two-pointer pattern.

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✨ Bonus Challenges (Optional but Recommended)

• LeetCode 26. Remove Duplicates from Sorted Array

• LeetCode 844. Backspace String Compare

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📊 Explore Visualization

Try two-pointer visualizations at:
👉 https://visualgo.net/en/list

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🧩 Concept Summary

• Two pointers are most useful for:

  • Sorted arrays

  • Reverse traversal

  • Sliding window (upcoming)

  • Partitioning logic