# How to Test if a Host Is Active

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:

# How to Redirect to a New Page

This is an example that shows how to redirect (forward) to a new page in PHP.

# POJ 2001 Shortest Prefixes Report

View the Problem.

This problem can be solved by 2 methods.

# POJ 1190 Birthday Cake Report

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.

# POJ 1838 Banana Report

View this problem on POJ: 1838 Banana.

This problem can be categorized as the Union-Find problem.

# POJ 2104 K-th Number Report

View the problem description here: 2104 K-th Number .

To solve this problem, you need to learn the following knowledge first.

• Segment Tree
• Binary Search
• Merge Sort

If you know all the above, it’s easy to solve this problem.

# Config File for Compaq Evo N610c on Gentoo

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.

# POJ 1990 MooFest Report

View this problem on POJ: 1990 MooFest.

Here is my resolution:

# POJ 2184 Cow Exhibition

This problem can be solved by two methods

• Deepth First Search (DFS)
• Dynamic Programming (DP)

# POJ 2231 Moo Volume

Here is my pseudo code

# Configuring Gentoo With English Interface and SCIM

To install SCIM, follow the following steps:

# STL Function: Binary_search()

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

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.

# Force the Mail.app to Use UTF-8 Encoding on Macintosh

Open a terminal, and run the following command:

# Replace All Strings in a File

Here is the script to replace all strings in a file.

# How to Use STL Sort?

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: