std::map::find - cppreference.com

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# std::map::find

From cppreference.com
< cpp‎ | container‎ | map

[edit template]

iterator find( const Key& key ); | (1) |
const_iterator find( const Key& key ) const; | (2) |
template< class K > iterator find( const K& x ); | (3) | (since C++14)
template< class K > const_iterator find( const K& x ) const; | (4) | (since C++14)

1,2) Finds an element with key equivalent to `key`.
3,4) Finds an element with key that compares equivalent to the value `x`. These templates only participate in overload resolution if the type Compare::is_transparent exists. They allow calling this function without constructing an instance of `Key`

### [edit] Parameters

key | - | key value of the element to search for
x | - | a value of any type that can be transparently compared with a key

### [edit] Return value

Iterator to an element with key equivalent to `key`. If no such element is found, past-the-end (see end()) iterator is returned.

### [edit] Complexity

Logarithmic in the size of the container.

### [edit] Example

Run this code

    #include <iostream>
    #include <map>

    int main()
    {
        std::map<int,char> example = {{1,'a'},{2,'b'}};

        auto search = example.find(2);
        if(search != example.end()) {
            std::cout << "Found " << search->first << " " << search->second << '\n';
        }
        else {
            std::cout << "Not found\n";
        }
    }

Output:

    Found 2 b

### [edit] See also

count | returns the number of elements matching specific key (public member function) [edit]
equal_range | returns range of elements matching a specific key (public member function) [edit]

### [edit] Example

Demonstrates the risk of accessing non-existing elements via operator [].

Run this code

    #include <string>
    #include <iostream>
    #include <map>

    int main()
    {
        std::map<std::string,int> my_map;
        my_map["x"] =  11;
        my_map["y"] = 23;

        auto it = my_map.find("x");
        if (it != my_map.end()) std::cout << "x: " << it->second << "\n";

        it = my_map.find("z");
        if (it != my_map.end()) std::cout << "z1: " << it->second << "\n";

        // Accessing a non-existing element creates it
        if (my_map["z"] == 42) std::cout << "Oha!\n";

        it = my_map.find("z");
        if (it != my_map.end()) std::cout << "z2: " << it->second << "\n";
    }

Output:

    x: 11
    z2: 0

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