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map find() function in C++ STL

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  • Difficulty Level : Easy
  • Last Updated : 06 Jul, 2022

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).

CPP-STL-Self-Paced-Course

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

Time Complexity: O(log n)
Auxiliary Space: O(n)

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