程序员ZZ的源码

真的了解树的定义吗？熟悉树在java中的实现吗？

看到堆，我们想到堆排序，以及延伸k个最大值和K个最小值；而在java中优先队列（PriorityQueue）很好实现了堆

栈在java中使用

Given an array of integers, return indices of the two numbers such that they add up to a specific target

Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. For example: ["2", "1", "+", "3", "*

Ｑ：Problem: Rotate an array of n elements to the right by k steps. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. How many different ways do you know to s