std::distance
| Defined in header  <iterator> | ||
| template< class InputIt > typename std::iterator_traits<InputIt>::difference_type  | ||
Returns the number of elements between first and last.
| The behavior is undefined if  | (until C++11) | |
| If  | (since C++11) | |
| Contents | 
[edit] Parameters
| first | - | iterator pointing to the first element | 
| last | - | iterator pointing to the end of the range | 
| Type requirements | ||
| - InputItmust meet the requirements ofInputIterator. The operation is more efficient ifInputItadditionally meets the requirements ofRandomAccessIterator | ||
[edit] Return value
The number of increments needed to go from first to last. The value may be negative if random-access iterators are used and first is reachable from last (since C++11)
[edit] Complexity
Linear.
However, if InputIt additionally meets the requirements of RandomAccessIterator, complexity is constant.
[edit] Example
#include <iostream> #include <iterator> #include <vector> int main() { std::vector<int> v{ 3, 1, 4 }; std::cout << "distance(first, last) = " << std::distance(v.begin(), v.end()) << '\n' << "distance(last, first) = " << std::distance(v.end(), v.begin()) << '\n'; }
Output:
distance(first, last) = 3 distance(last, first) = -3
[edit] See also
| advances an iterator by given distance (function) | 


