Next Spaceship

Driving into future…

How to Test if a Host Is Active

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Sometimes, we would like to check if a remote host is reachable before we establish a connection. This is much like the function of the ping command in terminal. Well in Cocoa programing, you can use the function SCNetworkReachabilityCreateWithName().

Here is the code:

POJ 1190 Birthday Cake Report

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View this problem on POJ: 1190 Birthday Cake (生日蛋糕)

There is no good methods, maybe dynamic programing is feasible, but it’s too complex for me to construct the transformation equation.

I have to use DFS (Depth First Search) to solve this problem. After the TLE (Time Limit Exceeds) appeared enough times, I worked it out. Pruning is very important for this problem.

Config File for Compaq Evo N610c on Gentoo

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Wow, Compaq Evo N610c…It’s really an old machine… I searched the configure file for this machine, and fond only one page, but it’s too old to work for the latest Gentoo system. Here is my configure file, which costs me days of work.

STL Function: Binary_search()

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In some cases, we just want to if an element exists in a sorted list, then we can use the STL function: binary_search(). To use this function, you must include the header <algorithm>. Note before we use binary_search(), the list must be sorted, either in ascending order or in descending order. …… Here is a simpler example explaining how to use this function.

__int64 vs Long Long

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long long is a standard C++ type, so if you use gcc, you can use this type without any problem. But on Windows, as some old Microsoft C++ compilers don’t support the type long long, you have to use the non-standard type: __int64.

The following example shows how to input and output an __int64 type of variable.

How to Use STL Sort?

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By now, the fastest comparison sorting algorithm is \(Ο(N\log N)\). The sort() function in STL implemented with an optimized quicksort, which is always \(O(N\log N)\).

Here is an example:

How to Use “Pair” in STL?

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In Python, we have tuple, and in Java, we have Map, but in C++, the language itself doesn’t contain anything equivalent. Nevertheless, we can use STL - the Standard Template Library - to construct the data structure.

Of course, we can construct this by ourself, and it’s not complex, but as we will see, with “pair” we can make it easier and simpler.

This is an example: