Two pointers: trapping rain water

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Task

📝 **Question:** Implement `trap(h)` in O(n) with two pointers. Test on [0,1,0,2,1,0,1,3,2,1,2,1] → 6.

📋 Pick the right answer.

💡 **Hint:** Re-read the theory above if unsure.

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🎯write

Heaps: median from a stream

🎯writeFREE

Two pointers: pair sum

🎯write

Two pointers: palindrome check

🤖predictFREE

Prerequisites — what you should know before this track

⚡predictFREE

Prerequisites — what you should know before this track

✏️ Write your code here

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📊 Result

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💬 Discussion