C++ for_each()
C++ 算法函数for_each()
C++ 算法for_each()函数将函数func应用于从"第一个"到"last"范围内的所有元素。
语法
template <class InputIterator, class Function>
Function for_each (InputIterator first, InputIterator last, Function func);
参数
first: 它指定列表中的第一个元素。
last : 它指定列表中的last元素。
func : 这是一元函数，接受范围内的参数。
返回值
该函数返回'func'。
示例1
#include <iostream>
#include <algorithm>
#include <vector>
void newfunction (int k)
{
std::cout << " " <<k;
}
struct newclass
{
void operator () (int k)
{
std::cout <<" "<<k;
}
}
newobject;
int main()
{
std::vector<int> newvector;
newvector.push_back(50);
newvector.push_back(100);
newvector.push_back(150);
std::cout << "newvector contains:\n";
for_each (newvector.begin () , newvector.end (), newfunction);
std::cout<< "\n newvector contains:\n";
for_each (newvector.begin (), newvector.end(), newfunction);
std::cout<<"\n";
return 0;
}
输出:
newvector contains: 50 100 150
newvector contains: 50 100 150
示例2
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void printx1(int b)
{
cout << b * 2 << " ";
}
struct Class1
{
void operator() (int b)
{
cout << b * 3 << " ";
}
} obj1;
int main()
{
int ar[5] = { 6, 7, 8, 9, 10 };
cout << "Using Arrays:" << endl;
cout << "Multiple of 2 of elements are : ";
for_each(ar, ar + 5, printx1);
cout << endl;
cout << "Multiple of 3 of elements are : ";
for_each(ar, ar + 5, obj1);
cout << endl;
vector<int> ar1 = { 2,3,5,7,1 };
cout << "Using Vectors:" << endl;
cout << "Multiple of 2 of elements are : ";
for_each(ar1.begin(), ar1.end(), printx1);
cout << endl;
cout << "Multiple of 3 of elements are : ";
for_each(ar1.begin(), ar1.end(), obj1);
cout << endl;
}
输出:
Using Arrays:
Multiple of 2 of elements are : 12 14 16 18 20
Multiple of 3 of elements are : 18 21 24 27 30
Using Vectors:
Multiple of 2 of elements are : 4 6 10 14 2
Multiple of 3 of elements are : 6 9 15 21 3
复杂度
该函数以线性方式移动，从第一个元素开始到last元素。对于列表中的每个元素，都会检查" pred"的值。搜索一直进行到与" pred？"不匹配为止。
数据竞争
该函数可以访问指定范围内的所有对象或其中的某些对象。
异常
如果任何参数抛出一个异常，则该函数将引发异常。
