Torstan

摘要： 问题：一副扑克牌54张，随机打乱之后排成一叠，从上到下一次翻（摸）一张牌，直到翻到一张k为止。问:下一张牌是黑桃k的概率大还是黑桃3的概率大？分析一下这个题目，可以发现题目有歧义（既然是条件概率，那已知的条件有哪些呢？）：题目理解1。如果只有一个人在翻牌，那他肯定知道第一张k是不是黑k，也肯定知道黑3有没有翻出来，也肯定知道还剩多少张牌。有了这些数据，算下一张牌是黑3还是黑k的概率就容易些了。题目理解2。如果有两个人，一个人翻牌，另一个人不许看。当翻牌的人翻出了第一张k，而且不告诉另一个人是什么k，且不告诉他翻了多少张之类的。仅仅告诉另一个人翻出了一张k。这时问另外一个人下一张牌是黑3的概率大 阅读全文

摘要： mutex and condition variable 阅读全文

摘要： Virtual inheritance is used to solve the problem of diamonds inheritance, 2 instance of base objects, in multiple inheritance. With the knowledge on c++ object model, we can understand virtual inheritance easily. Here is a sample code.#include<iostream>using namespace std;class Point2D_IF{ pub 阅读全文

摘要： code 1.#include <iostream>using namespace std;class Base { public: Base() {cout<<"Base constructor"<<endl;} ~Base() {cout<<"Base destructor"<<endl;}};class Derived:public Base{ public: Derived() {cout<<"Derived constructor"<<end 阅读全文

摘要： Thread local storage allows multi-threaded applications to have a separate instance of a given data item for each thread. Where a single-threaded application would use static or global data, this could lead to contention, dead lock or data corruption in a multi-threaded application. One example is t 阅读全文

摘要： Definition 1. Let A and B be sets. A binary relation from A to B is a subset of A X B.In other words, a binary relation from A to B is a set R of ordered pair in which the first element of each ordered pair comes from A and the second element comes from B. We use aRa to denote that (a, b) belongs to 阅读全文

摘要： 1. Mathematical inductionMathematical induction can be used to prove the statement that asserts P(n) is true for all positive integers n, where P(n) i... 阅读全文

摘要： 题目1. 给定一个包含n行数据的文件（n未知），要求设计一个算法，只遍历文件一遍就能等概率地输出某一行。即，每行被输出的概率是相等的（1/n，n未知）。假设文件可能会很大，内存有限，不能保存所有的文件数据。题目2. n个数据排除一行，即数据Ci在位置Li, 1<=i<=n，设计一个算法把数据打乱，使得每个数据在等概率地出现在每个位置，即 p(Ci, Lj)=1/n, 其中 1<=i<=n, 1<=j<=n.答案见下方-------------------------------------------------------------------解答1.【 阅读全文

摘要： What is this topic about?It is a study on the difference betweeen a function returning a vector and a function accepting a reference to a vector as a parameter.[torstan]$ more vec.cc#include<vector>using namespace std;vector<int> f(){ vector<int> v; v.push_back(2); return v;}/*g++ 阅读全文

摘要： 1) BackgroundSometimes, when we meet with a problem very hard to explain or understand, we can try more powerful tools, e.g. math or assembly code. In... 阅读全文