Implement a trie with insert, search, and startsWith methods. Example12345678Trie trie = new Trie();trie.insert("apple");trie.search("apple"); // re ...

Java类库中的java.util.Observer接口和java.util.Observable类就是一种Observer模式。 java.util.Observer接口中定义了一下方法。 1public void update(Observable obj, Object arg) 而upda ...

Given a 2D matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2) ...

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. The update(i, val) function modifies nums by upd ...

当观察对象的状态发生变化时，会通知给观察者。适用于根据对象状态进行相应处理的场景。 示例观察者将观察一个会生成数值的对象，并将它生成的数值结果显示出来。不同的观察者的显示方式不一样。 类图 Observer接口123public interface Observer { public ...

组员向仲裁者报告，仲裁者向组员下达指示。组员之间不再相互询问和相互指示。 示例一个GUI应用程序，它展示了一个登录对话框，用户在其中输入正确的用户名和密码后可以登录。 可以选择作为游客访问（Guest）或是作为用户登录（Login） 作为用户登录时，需要输入正确的用户名（Username）和密码（ ...

Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2 ...

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. ExampleGiven nums = [-2, 0, 3, -5, 2, -1] sumRan ...

You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 ston ...

Given an array nums, write a function to move all 0’s to the end of it while maintaining the relative order of the non-zero elements. ExampleInput: [0 ...