James Pan

原题网址：https://leetcode.com/problems/best-time-to-buy-and-sell-stock/ Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to comple

原题网址：https://leetcode.com/problems/min-stack/ Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) -- Push element x onto stack.pop() -- Re