Is the Iteration Order of Elements in a std::map Guaranteed?

Guaranteed Ordering of std::map Iterations

In a std::map, elements are sorted according to their keys, ensuring an ascending order of key values. This characteristic raises the question of whether the iteration order of elements through std::map iterators is also guaranteed in terms of key values.

Answer:

Yes, the iteration order is guaranteed by the C standard. When iterating from std::map::begin() to std::map::end(), elements will be traversed in ascending order of key values.

Example:

Consider the following code snippet:

<code class="cpp">std::map<int int> map_;
map_[1] = 2;
map_[2] = 3;
map_[3] = 4;
for( std::map<int int>::iterator iter = map_.begin();
     iter != map_.end();
     ++iter )
{
    std::cout second;
}</int></int></code>

This code will guaranteedly print 234, as the iteration order is guaranteed to follow the sorted keys 1, 2, 3.

Implications:

This ordering is not a mere coincidence but a fundamental aspect of std::map. It is utilized for determining when two key values are considered equal and for efficient logarithmic-complexity binary searches.

Conclusion:

The iteration order of std::map ensures consistent and reliable access to elements in ascending order of key values. This guarantees efficient and predictable operation.

The above is the detailed content of Is the Iteration Order of Elements in a std::map Guaranteed?. For more information, please follow other related articles on the PHP Chinese website!