C++算法库 (3)划分操作

/*is_partitioned   检测某个范围是否按指定谓词划分过*/#include <iostream>#include <algorithm>#include <array>using namespace std;bool IsOdd(int i) {return (i % 2) == 1;}int main(int argc, const char * argv[]){    array<int, 7> foo = {1,2,3,4,5,6,7};        //print contents:    cout<<"foo:";    for (int& x:foo)        cout<<" "<<x;    if (is_partitioned(foo.begin(), foo.end(), IsOdd))        cout<<" (partitioned)"<<endl;    else        cout<<" (not partitioned)"<<endl;            //partition array:    partition(foo.begin(), foo.end(), IsOdd);        //print contents again:    cout<<"foo:";    for (int& x:foo)        cout<<" "<<x;    if (is_partitioned(foo.begin(), foo.end(), IsOdd))        cout<<" (partitioned)"<<endl;    else        cout<<" (not partitioned)"<<endl;    return 0;}

输出结果：

foo: 1 2 3 4 5 6 7 (not partitioned)foo: 1 7 3 5 4 6 2 (partitioned)

/*partition   将某个范围划分为两组*/#include <iostream>#include <algorithm>#include <vector>using namespace std;bool IsOdd(int i) {return (i % 2) == 1;}int main(int argc, const char * argv[]){    vector<int> myvector;    vector<int>::iterator it;    //set some values:    for (int i = 1; i < 10; ++i)        myvector.push_back(i);        vector<int>::iterator bound;    bound = partition(myvector.begin(), myvector.end(), IsOdd);        //print out content:    cout<<"odd elements:";    for (it = myvector.begin(); it != bound; ++it)        cout<<" "<<*it;    cout<<endl;        cout<<"even elements:";    for (it = bound;it != myvector.end(); ++it )        cout<<" "<<*it;    cout<<endl;        return 0;}

输出结果：

odd elements: 1 9 3 7 5even elements: 6 4 8 2

/*partition_copy   拷贝指定范围的划分结果*/#include <iostream>#include <algorithm>#include <vector>using namespace std;bool IsOdd(int i) {return (i % 2) == 1;}int main(int argc, const char * argv[]){    vector<int> foo;    vector<int> odd,even;        vector<int>::iterator it;        //set some values:    for (int i = 1; i < 10; ++i)        foo.push_back(i);        unsigned n = (unsigned)count_if(foo.begin(), foo.end(), IsOdd);    odd.resize(n);    even.resize(foo.size() - n);        //partition:    partition_copy(foo.begin(), foo.end(), odd.begin(), even.begin(), IsOdd);            //print contents:    cout<<"odd: ";    for (int& x:odd)        cout<<" "<<x;    cout<<endl;        cout<<"even: ";    for (int& x:even)        cout<<" "<<x;    cout<<endl;                        return 0;}

输出结果：

odd:  1 3 5 7 9even:  2 4 6 8

/*partition_point    返回被划分范围的划分点*/#include <iostream>#include <algorithm>#include <vector>using namespace std;bool IsOdd(int i) {return (i % 2) == 1;}int main(int argc, const char * argv[]){    vector<int> foo;    vector<int> odd;            //set some values:    for (int i = 1; i < 10; ++i)        foo.push_back(i);    partition(foo.begin(), foo.end(), IsOdd);        auto it = partition_point(foo.begin(), foo.end(), IsOdd);    odd.assign(foo.begin(), it);        //print contents of odd:    cout<<"odd:";    for (int& x:odd)        cout<<" "<<x;    cout<<endl;        return 0;}

输出结果：

odd: 1 9 3 7 5

/*stable_partition    稳定划分，两组元素各维持相对顺序*/#include <iostream>#include <algorithm>#include <vector>using namespace std;bool IsOdd(int i) {return (i % 2) == 1;}int main(int argc, const char * argv[]){    vector<int> myvector;    vector<int>::iterator it;    vector<int>::iterator bound;            for (int i = 1; i < 10; ++i)        myvector.push_back(i);        bound = stable_partition(myvector.begin(), myvector.end(), IsOdd);        //print out content:    cout<<"odd elements:";    for (it = myvector.begin(); it != bound  ; ++it)        cout<<" "<<*it;    cout<<endl;        cout<<"even elements:";    for (it = bound; it != myvector.end(); ++it)        cout<<" "<<*it;    cout<<endl;    return 0;}

输出结果：

odd elements: 1 3 5 7 9even elements: 2 4 6 8