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C++ Unordered_map Library - operator== Function
Description
The C++ function std::unordered_map::operator== tests whether two unordered_maps are equal or not.
Declaration
Following is the declaration for std::unordered_map::operator== function form std::unordered_map header.
C++11
template <class Key, class T, class Hash, class Pred, class Alloc> bool operator==(const unordered_map<Key,T,Hash,Pred,Alloc>& first, const unordered_map<Key,T,Hash,Pred,Alloc>& second );
Parameters
first − First unordered_map object.
second − Second unordered_map object.
Return value
Returns true if both unordered_map are equal otherwise false.
Time complexity
Linear i.e. O(n) in average case.
Quadratic i.e. O(n2) in worst case.
Example
The following example shows the usage of std::unordered_map::operator== function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_map<char, int> um1; unordered_map<char, int> um2; if (um1 == um2) cout << "Both unordered_maps are equal" << endl; um1.emplace('a', 1); if (!(um1 == um2)) cout << "Both unordered_maps are not equal" << endl; return 0; }
Let us compile and run the above program, this will produce the following result −
Both unordered_maps are equal Both unordered_maps are not equal
unordered_map.htm
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