cb39a_c++_STL_算法_for_each_transform_比较

cb39a_c++_STL_算法_for_each_transform_比较
for_each() 速度快，不灵活
transform() 速度慢， 非常灵活

STL算法-修改性算法
for_each()
copy()
copy_backward()
transform()
merge()
swap_ranges()
fill()
fill_n()

generate()
generate_n()
replace()
replace_if()
replace_copy()
replace_copy_if()

void square(int &elem)//for_each参数必须是按引用传递，速度快
{
elem = elem*elem;

}
int square2(int elem)//transform不能传引用，传copy，速度慢
{
return elem * elem;
}

int main()
transform(b.begin(), b.end(), b.begin(), square2);

 /*cb39a_c++_STL_算法_for_each_transform_比较
 for_each() 速度快，不灵活
 transform() 速度慢， 非常灵活

 STL算法-修改性算法
 for_each()
 copy()
 copy_backward()
 transform()
 merge()
 swap_ranges()
 fill()
 fill_n()

 generate()
 generate_n()
 replace()
 replace_if()
 replace_copy()
 replace_copy_if()

 void square(int &elem)//for_each参数必须是按引用传递，速度快
 {
     elem = elem*elem;

 }
 int square2(int elem)//transform不能传引用，传copy，速度慢
 {
     return elem * elem;
 }

 int main()
 transform(b.begin(), b.end(), b.begin(), square2);
 */

 #include <iostream>
 #include <algorithm>
 #include <vector>

 using namespace std;
 void square(int &elem)//for_each参数必须是按引用传递，速度快
 {
     elem = elem*elem;

 }
 int square2(int elem)//transform不能传引用，传copy，速度慢
 {
     return elem * elem;
 }

 int main()
 {
     vector<int> a;
     vector<int> b;
     for (int i = ; i <= ; ++i)
     {
         a.push_back(i);
         b.push_back(i);
     }
     cout << "向量a:" << endl;
     for (vector<int>::iterator iter = a.begin(); iter != a.end(); ++iter)
         cout << *iter << ' ';
     cout << endl;
     cout << "使用for_each" << endl;
     for_each(a.begin(), a.end(), square);//调用square函数
     for (vector<int>::iterator iter = a.begin(); iter != a.end(); ++iter)
         cout << *iter << ' ';
     cout << endl;

     cout << "向量b:" << endl;
     for (vector<int>::iterator iter = b.begin(); iter != b.end(); ++iter)
         cout << *iter << ' ';
     cout << endl;

     cout << "使用transform算法,不能传引用" << endl;
     transform(b.begin(), b.end(), b.begin(), square2);

     for (vector<int>::iterator iter = b.begin(); iter != b.end(); ++iter)
         cout << *iter << ' ';
     cout << endl;

     return ;
 }