Write a SQL query to find all duplicate emails in a table named Person.
A peak element is an element that is greater than its neighbors.
Compare two version numbers version1 and version2.If version1 > version2 return 1; if version1 < version2 return -1;otherwise return 0.
Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.
Given a positive integer, return its corresponding column title as appear in an Excel sheet.
Given a column title as appear in an Excel sheet, return its corresponding column number.
Given an integer n, return the number of trailing zeroes in n!.
Given a linked list, return the node where the cycle begins. If there is no cycle, return null.
Given a binary tree, return the preorder traversal of its nodes’ values.
Given a binary tree, return the postorder traversal of its nodes’ values.
