function template
<unordered_set>
std::operators (unordered_set)
| equality (1) | template <class Key, class Hash, class Pred, class Alloc> bool operator== ( const unordered_set<Key,Hash,Pred,Alloc>& lhs, const unordered_set<Key,Hash,Pred,Alloc>& rhs ); |
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| inequality (2) | template <class Key, class Hash, class Pred, class Alloc> bool operator!= ( const unordered_set<Key,Hash,Pred,Alloc>& lhs, const unordered_set<Key,Hash,Pred,Alloc>& rhs ); |
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Relational operators for unordered_set
These overloaded global operator functions perform the appropriate equality or inequality comparison operation between the unordered_set containers lhs and rhs.
The procedure for the equality comparison is as follows (stopping at any point if the procedure finds a conclusive answer):
- First, the sizes are compared.
- Then, each element in one of the containers is looked for in the other.
Note that the unordered_set::hash_function and unordered_set::key_eq objects are expected to have the same behavior in both lhs and rhs.
Parameters
- lhs, rhs
- unordered_set containers (to the left- and right-hand side of the operator, respectively), having both the same template parameters (Key, Hash, Pred and Alloc).
Return Value
true if the condition holds, and false otherwise.
Example
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// unordered_set comparisons
#include <iostream>
#include <string>
#include <unordered_set>
int main ()
{
std::unordered_set<std::string>
a = {"AAPL","MSFT","GOOG"},
b = {"MSFT","GOOG","AAPL"},
c = {"MSFT","GOOG","AAPL","ORCL"};
if (a==b) std::cout << "a and b are equal\n";
if (b!=c) std::cout << "b and c are not equal\n";
return 0;
}
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Output:
a and b are equal
b and c are not equal
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Complexity
Average case: linear in size.
Worst case: quadratic in size.
Iterator validity
No changes.