How to Efficiently Find Specific Monsters in a Vector of Structs using C ?

Finding Monsters in a Vector

When searching through a vector of custom structs, you may encounter difficulties in isolating and iterating over specific elements. This article explores a solution to this problem using C 's standard library functions.

Problem:

Consider the following struct:

<code class="cpp">struct monster {
    DWORD id;
    int x;
    int y;
    int distance;
    int HP;
};</code>

Creating a vector of these structs:

<code class="cpp">std::vector<monster> monsters;</code>

You wish to search for a specific monster within the vector based on its id element.

Solution:

To search for an element based on a specific field, use the std::find_if function instead of std::find. std::find_if allows you to specify a predicate function that filters the elements of the vector.

Here are two ways to approach this using std::find_if:

1. Using Boost Libraries:

If you have Boost libraries available, you can use the following code:

<code class="cpp">it = std::find_if(bot.monsters.begin(), bot.monsters.end(),
        boost::bind(&monster::id, _1) == currentMonster);</code>

2. Creating a Custom Function Object:

If you don't have Boost, create a custom function object as follows:

<code class="cpp">struct find_id : std::unary_function<monster, bool> {
    DWORD id;
    find_id(DWORD id) : id(id) {}
    bool operator()(monster const& m) const {
        return m.id == id;
    }
};</code>

Then use this function object in std::find_if:

<code class="cpp">it = std::find_if(bot.monsters.begin(), bot.monsters.end(),
         find_id(currentMonster));</code>

This will iterate through the monsters vector and search for the monster with the specified id. The iterator it returned by std::find_if can then be used to access the found monster.

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