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unordered_multimap reserve() function in C++ STL
The unordered_multimap reserve() function in C++ STL sets the number of buckets in the container to the most appropriate number so that it contains at least n elements.
If n is greater than the current numbers of bucket multiplied by the max_load_factor, the container’s number of buckets is increased and a rehash is forced.
Reserve () returns nothing and take n as a parameter which specifies the minimum number of elements as per requested minimum capacity.
Algorithm
Begin Declare the vector m. m.reserve(6) = the size is reserved for the bucket to contain minimum number of one elements. Insert the key value pairs. Print the result. End.
Example Code
#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main() {
unordered_map<char, int> m; //declaring m as map container
m.reserve(6);//restricting the most appropriate value of
m.insert (pair<char, int>('b', 10)); // inserting values
m.insert (pair<char, int>('a', 20));
cout << "The size is: " << m.size();
cout << "\nKey and values are: ";
for (auto it = m.begin(); it != m.end(); it++) {
cout << "{" << it->first << ", " << it->second << "} "; //printing the values of map container
}
return 0;
}Output
The size is: 2
Key and values are: {a, 20} {b, 10}
Updated on: 30-Jul-2019
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