Torstan

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

摘要：This night, I downloaded the source code of Tcmalloc after supper, and studied it for several hours. I am recording some findings here in case that I forget them tommorow.1. File libc_override_gcc_and_weak.h does override malloc routines (malloc, free, realloc, and so on) on systems that define the 阅读全文

摘要：Q1. give a recursive definition for the set of ordered pair of positive intergers, S={(a, b)| a, b are positive intergers, and a|b}Answer:basis step: (1, 1) belongs to S;recursive step: if (a, b)belongs to S, (a, a+b) belongs to S, and (a+1, a+1) belongs to S. 阅读全文

摘要：Assume there is a polygon (v1, v2,...vn), where vi, (1<=i<=n) are its vertices. What is the area of this polygon?We have learnt cross product, which can be used to calculate the area of a triangle. We can also use this to calculate the area of a polygon by dividing the polygon with n segments 阅读全文

摘要：I have made a more sophisticated version ofmemory allocator based on mmap. It can avoid memory increacement issue happened in traditional memory allocator, e.g. glibc malloc/free. However, it has two disadvantages. One of them is that this allocator is slower than glibc malloc/free since it call mma 阅读全文

摘要：有一道样的题：三个杯子，一个13L，装了10L水；一个7L,装了2L水；一个6L,装了3L水，问怎样倒，使得3个杯子各有5L水。没有其它任何工具，杯子上没有刻度，不能倒出1/2,1/3之类的。请问怎么倒？ 如果不能做到，请证明。解答：不能做到。[引理]从A杯子倒水到B杯子，只能把A里面的水全部倒完，或者把B杯子倒满。[证明]假设能做到，最后一步是这样的：有一个杯子A装了5升，另外一个杯子B有一些水，还剩一个杯子C有一些水，假设从B倒水到C，使得B和C都有5升水。另一方面，从B倒水到C只有两种方式，把B倒空，或者把C倒满。第一种方式，把B倒空，显然做不到每个杯子5升水，因为B剩下0升，且这是最后 阅读全文