https://leetcode.com/problems/valid-palindrome/
https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/
https://leetcode.com/problems/remove-duplicates-from-sorted-array/
https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/
https://leetcode.com/problems/container-with-most-water/
https://leetcode.com/problems/trapping-rain-water/