STL algorithm is_partitioned (26)

Is_partitioned prototype:

STD: is_partitioned

template <class InputIterator, class UnaryPredicate>  bool is_partitioned (InputIterator first, InputIterator last, UnaryPredicate pred);

Whether the elements in the test scope are classified based on Pred. If yes, true is returned; otherwise, false is returned.

Division means that PRED (* It) is performed on each element, and whether the values of true and false in the result are a division.

For example, t f, t, f, or f t is a division.

However, t f t or f t f is not a division.

The behavior is as follows: (this behavior seems to be a bit problematic. For example, if the division is fffttt, it seems that false is returned)

template <class InputIterator1, class InputIterator2>  bool is_partitioned (InputIterator1 first, InputIterator1 last, UnaryPredicate pred){  while (first!=last && pred(*first)) {    ++first;  }  while (first!=last) {    if (pred(*first)) return false;    ++first;  }  return true;}

A simple example:

#include <iostream>#include <vector>#include <array>#include <algorithm>using namespace std;void ispartitioned2(){    vector<int> vi{1,3,5,7,9,8,6,10,12};    cout<<"vi=";    for_each(vi.begin(),vi.end(),[](int i){cout<<i<<" ";});    cout<<endl;    if(is_partitioned(vi.begin(),vi.end(),[](int n){return n%2!=0;}))        cout<<"v1 is a partitioned!"<<endl;    else        cout<<"v1 not a partitioned!"<<endl;    vector<int> v2{2,4,6,8};    cout<<"v2=";    for_each(v2.begin(),v2.end(),[](int i){cout<<i<<" ";});    cout<<endl;    if(is_partitioned(v2.begin(),v2.end(),[](int n){return n%2!=0;}))        cout<<"v2 is a partitioned!"<<endl;    else        cout<<"v2 not a partitioned!"<<endl;    vector<int> v3{1,3,4,6,8};    cout<<"v3=";    for_each(v3.begin(),v3.end(),[](int i){cout<<i<<" ";});    cout<<endl;    if(is_partitioned(v3.begin(),v3.end(),[](int n){return n%2!=0;}))        cout<<"v3 is a partitioned!"<<endl;    else        cout<<"v3 not a partitioned!"<<endl;    vector<int> v4{1,2,5,4,6,8};    cout<<"v4=";    for_each(v4.begin(),v4.end(),[](int i){cout<<i<<" ";});    cout<<endl;    if(is_partitioned(v4.begin(),v4.end(),[](int n){return n%2!=0;}))        cout<<"v4 is a partitioned!"<<endl;    else        cout<<"v4 not a partitioned!"<<endl;}

Run:

We can see that V3 belongs to the ffttt type, but it is still a division!

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Author: unparalleled

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Yu gdut

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STL algorithm is_partitioned (26)