unordered_map find in C++ STL (original) (raw)

Last Updated : 26 Sep, 2024

In C++, **std::unordered_map::find function is used to search for a specific element using the key in an unordered map container. It is a member function of std::unordered_map container defined inside <unordered_map> header file.

**Syntax

um.**find(key);

**Parameters

• **key: The key of the element to be searched.

**Return Value

• If the given key is found, it returns an iterator to that pair.
• Otherwise, it returns the end iterator.

Example of unordered_map::find()

C++ `

// C++ program to demonstrate how to use // unordered_map::find() function #include <bits/stdc++.h> using namespace std;

void checkKey(unordered_map<int, string>& um, int key) { // Searching for element with key if (um.find(key) == um.end()) cout << "Key " << key << " Not Present\n"; else cout << "Key " << key << " Present\n"; }

int main() { unordered_map<int, string> um = {{12, "Geeks"}, {678, "Geeksfor"}, {88, "Gfg"}};

// Key1 and key2 which have to search
int key1 = 678;
int key2 = 456;

  checkKey(um, key1);
  checkKey(um, key2);
return 0;

}

`

Output

Key 678 Present Key 456 Not Present

**Time Complexity: O(1) on average. O(n) in worst case where n is the number of elements.
**Space Complexity: O(1)