C++ Unordered_map Library - find() Function


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Description

The C++ function std::unordered_map::find() finds an element associated with key k.

If operation succeeds then methods returns iterator pointing to the element otherwise it returns an iterator pointing the map::end().

Declaration

Following is the declaration for std::unordered_map::find() function form std::unordered_map header.

C++11

iterator find (const key_type& k);
const_iterator find (const key_type& k) const;

Parameters

k − Key to be searched.

Return value

If object is constant qualified then method returns a constant iterator otherwise non-constant iterator.

Time complexity

Constant i.e. O(1) in average case.

Linear i.e. O(n) in worst case.

Example

The following example shows the usage of std::unordered_map::find() function.

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_map<char, int> um = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5}
            };

   auto it = um.find('d');

   cout << "Iterator points to " << it->first
       << " = " << it->second << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Iterator points to d = 4
unordered_map.htm
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