DAY 18 Solving Complex Two-Pointer Problems

Hello Everyone!

I am Somuya Khandelwal, back with updates from Day 3 of Week 4 in my competitive programming journey. Today’s focus was on Two-Pointer Problems, a technique often used to optimize array and string traversal. These problems challenged me to think critically about efficiency and edge case handling while maintaining clean and concise code.

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What I Worked On Today

1. Text Justification (Hard Difficulty)

   • Given an array of words and a max width, format the text so each line is fully justified.
   • Approach:
     • Used a two-pointer approach to group words that fit within the max width.
     • Balanced spaces between words and handled edge cases like the last line or single-word lines.
   • What I Learned:
     • Problems with formatting constraints require a systematic approach to divide tasks into logical steps.
     • Handling edge cases like single-word lines and trailing spaces is crucial for correctness.

2. Container With Most Water (Medium Difficulty)

   • Find two lines in an array that form a container with the most water.
   • Approach:
     • Used the two-pointer technique, starting with pointers at the beginning and end of the array.
     • Moved the pointer with the smaller height inward to maximize the area.
   • What I Learned:
     • The two-pointer technique is ideal for optimization problems involving sorted or semi-sorted data.
     • Focusing on the limiting factor (the smaller height in this case) simplifies the solution.

3. 3 Sum (Medium Difficulty)

   • Find all unique triplets in an array that sum to zero.
   • Approach:
     • Sorted the array and fixed one number, using two pointers to find pairs that sum to the negative of the fixed number.
     • Skipped duplicate numbers to avoid redundant triplets.
   • What I Learned:
     • Sorting combined with the two-pointer technique reduces time complexity for problems involving multiple constraints.
     • Managing duplicates efficiently ensures that the solution is both correct and optimal.

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What I Learned Today

1. The Power of Two-Pointer Techniques:

   • Problems like Container With Most Water and 3 Sum highlight the efficiency of two-pointer approaches for reducing brute-force complexity.

2. Handling Edge Cases in Formatting:

   • Text Justification taught me how to handle various formatting requirements, such as balancing spaces and dealing with single-word lines.

3. Combining Sorting and Two Pointers:

   • Sorting arrays before applying the two-pointer technique simplifies logic and reduces the need for additional checks.

4. Debugging Complex Logic:

   • Problems with multiple conditions, like Text Justification, require careful debugging to ensure all edge cases are handled correctly.

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Reflections and Challenges

The Text Justification problem was particularly challenging because it required combining logical grouping with precise formatting. Debugging space distribution and last-line handling took considerable effort but was extremely rewarding. The 3 Sum problem emphasized the importance of managing duplicates efficiently, which added an extra layer of complexity.

Overall, today’s challenges reinforced the value of the two-pointer technique and sharpened my problem-solving skills for array-based optimization problems.

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Looking Ahead

Tomorrow, I’ll work on Sliding Window Problems, including Substring With Concatenation of All Words and Minimum Window Substring. These tasks will test my ability to manage dynamic windows and solve substring-related challenges efficiently.

Thank you for following along on my journey! Stay tuned for more updates and learnings as I continue to grow in competitive programming.