Determine whether an integer is a palindrome. Do this without extra space.
Given an integer, convert it to a roman numeral.
Given n non-negative integers $a1, a2, …, an$, where each represents a point at coordinate $(i, ai)$. $n$ vertical lines are drawn such that the two endpoints of line $i$ is at $(i, ai)$ and $(i, 0)$. Find two lines, which together with x-axis forms a container, such that the container contains the most water.
Implement atoi to convert a string to an integer.
Reverse digits of an integer.
The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)