Solving Trapping Rain Water using Two pointers.

Problem

Water trapped between bars.

Pattern

This problem demonstrates the Two pointers pattern.

Approach

Track left/right max heights.

Solution 

  // Solution for Trapping Rain Water
// Pattern: Two pointers
// O(n) time, O(1) space

Complexity

O(n) time, O(1) space

Best Practices

  • Identify the pattern before coding — pattern recognition saves time
  • Handle edge cases: empty input, single element, duplicates
  • Use descriptive variable names even in timed interviews
  • Test with the provided examples plus one custom case