map find() function in C++ STL

The std::map::find() is a built-in function in C++ STL that is used to find an element with given key in the map. It is a member function of std::map container so we can directly use it with any map.

Syntax

map_name.find(key)

Parameters

key: Key of the pair to be searched in the map container.

Return Value

If the key is found, it returns an iterator to the position where the key is present in the map.
If the key is not found, it returns an iterator to the end of the map.

Example of map::find()

C++

// C++ program for illustration of map::find()
// function
#include <bits/stdc++.h>
using namespace std;

int main() {

    // Creating a map
    map<int, int> mp;
    mp.insert({2, 30});
    mp.insert({1, 40});
    mp.insert({3, 20});
    mp.insert({4, 50});

    // key1 find (exist in the map)
    int key1 = 2;

    // key2 find (does not exist in the map)
    int key2 = 5;

  	auto it = mp.find(key1);
  
    // Check if key1 is found
    if (it != mp.end()) {
        cout << "Key '" << it->first << "' found with";
        cout << " value: " << it->second << endl;
    }

    // Element not present
    else
        cout << "Key '" << key1 << "' not found!" << endl;

  	it = mp.find(key2);
  
    // Check if key2 is found
    if (it != mp.end()) {
        cout << "Key '" << it->first << "' found with";
        cout << " value: " << it->second;
    }

    // key2 not found
    else
        cout << "Key '" << key2 << "' not found!";

    return 0;
}

Output

Key '2' found with value: 30
Key '5' not found!

Complexity Analysis of map::find()

std::map container in C++ is implemented using some Balanced Binary Search Tree (mostly R-B Tree). So,

Time Complexity: O(log n), where n is the number of elements.
Auxiliary Space: O(1)