STL algorithm algorithms is_sorted and is_sorted_until (28)

The prototype of is_sort:

: Is_sorted

Default (1)	template <class ForwardIterator> bool is_sorted (ForwardIterator first, ForwardIterator last);
Custom (2)	template <class ForwardIterator, class Compare> bool is_sorted (ForwardIterator first, ForwardIterator last, Compare comp);

This function is used to test whether the elements in the range are ordered!

Use operator <or comp for comparison.

If the number of elements in the range is less than two, true is always returned.

The behavior is similar to the following:

123456789101112

template <class ForwardIterator> bool is_sorted (ForwardIterator first, ForwardIterator last){ if (first==last) return true; ForwardIterator next = first; while (++next!=last) { if (*next<*first) // or, if (comp(*next,*first)) for version (2) return false; ++first; } return true;}

A simple test example:

#include <iostream>#include <vector>#include <algorithm>using namespace std;int main(int argv,char **argc){vector<int> v1{1,2,3,4};vector<double> v2{4.0,5.0,3.5,6.0};cout<<"v1=";for(int i:v1)cout<<i<<" ";cout<<endl;if(is_sorted(v1.begin(),v1.end()))cout<<"v1 is sorted!"<<endl;elsecout<<"v1 is not sorted!"<<endl;cout<<"v2=";for(double i:v2)cout<<i<<" ";cout<<endl;if(is_sorted(v2.begin(),v2.end()))cout<<"v2 is sorted!"<<endl;elsecout<<"v2 is not sorted!"<<endl;}

Running result:

Is_sorted_until prototype:

STD: is_sorted_until

Default (1)	template <class ForwardIterator> ForwardIterator is_sorted_until (ForwardIterator first, ForwardIterator last);
Custom (2)	template <class ForwardIterator, class Compare> ForwardIterator is_sorted_until (ForwardIterator first, ForwardIterator last, Compare comp);

This function is similar to the relationship with is_heap and is_heap_until.

Returns the first element iterator that destroys sequence order.

Use operator <or comp for comparison.

Its behavior is similar:

234567891011

template <class ForwardIterator> ForwardIterator is_sorted_until (ForwardIterator first, ForwardIterator last){ if (first==last) return first; ForwardIterator next = first; while (++next!=last) { if (*next<*first) return next; ++first; } return last;}

A simple example:

#include <iostream>#include <vector>#include <algorithm>using namespace std;int main(int argv,char **argc){vector<int> v1{1,2,3,4,5};vector<double> v2{4.0,5.0,3.5,6.0,1.0};cout<<"v1=";for(int i:v1)cout<<i<<" ";cout<<endl;cout<<"v2=";for(double i:v2)cout<<i<<" ";cout<<endl;auto it=is_sorted_until(v1.begin(),v1.end());if(it==v1.end())cout<<"v1 is sorted!"<<endl;auto it2=is_sorted_until(v2.begin(),v2.end());cout<<"v2 the return is "<<*it2<<endl;}

Run:

By comparing the source code, we can know that the first return is v1.end (), and the second returns 3.5!

------------------------------------------------------------------

// For more instructions on writing errors or poor information, you can leave a message below or click the email address in the upper left corner to send an email to me, pointing out my errors and deficiencies, so that I can modify them, thank you for sharing it.

Reprinted please indicate the source: http://blog.csdn.net/qq844352155

Author: unparalleled

Email: [email protected]

Yu gdut

------------------------------------------------------------------

STL algorithm algorithms is_sorted and is_sorted_until (28)