map find() function in C++ STL

Difficulty Level : Easy
Last Updated : 28 Oct, 2020

The map::find() is a built-in function in C++ STL which returns an iterator or a constant iterator that refers to the position where the key is present in the map. If the key is not present in the map container, it returns an iterator or a constant iterator which refers to map.end().
Syntax:

iterator=map_name.find(key)
        or 
constant iterator=map_name.find(key)

Parameters: The function accepts one mandatory parameter key which specifies the key to be searched in the map container.

Return Value: The function returns an iterator or a constant iterator which refers to the position where the key is present in the map. If the key is not present in the map container, it returns an iterator or a constant iterator which refers to map.end().

Time Complexity for Searching element :
The time complexity for searching elements in std::map is O(log n). Even in the worst case, it will be O(log n) because elements are stored internally as Balanced Binary Search tree (BST) whereas, in std::unordered_map best case time complexity for searching is O(1).

Below is the illustration of the above function:

CPP

// C++ program for illustration
// of map::find() function
#include <bits/stdc++.h>
using namespace std;
 
int main()
{
 
    // Initialize container
    map<int, int> mp;
 
    // Insert elements in random order
    mp.insert({ 2, 30 });
    mp.insert({ 1, 40 });
    mp.insert({ 3, 20 });
    mp.insert({ 4, 50 });
 
    cout << "Elements from position of 3 in the map are : \n";
    cout << "KEY\tELEMENT\n";
 
    // find() function finds the position
    // at which 3 is present
    for (auto itr = mp.find(3); itr != mp.end(); itr++) {
       
        cout << itr->first << '\t' << itr->second << '\n';
    }
 
    return 0;
}

Output

The elements from position 3 in map are : 
KEY    ELEMENT
3    20
4    50

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