预定义函数对象和函数适配器案例

来源：互联网发布：aes加解密 java 编辑：程序博客网时间：2024/05/22 00:11
#include <iostream>      #include<string>      #include <vector>      #include <list>      #include <set>      #include <map>      #include <algorithm>      #include <functional>    using namespace std;   //函数对象class IsGreat{public:IsGreat(int n){this->n = n;}bool operator()(int i){if (i>n){return true;}return false;}protected:private:int n;};void display(){vector<int> v;int myarray[] = {10,20,20,20,30,40,50,60};for (int i =0;i<11;i++){v.push_back(i+1);}for (vector<int>::iterator it =v.begin();it!=v.end();it++){cout<<*it<<endl;}//统计 1在vector中出现的次数int num = count(v.begin(),v.end(),1);cout<<"num:"<<num<<endl;//统计数组myarray中20出现的次数int num2 = count(myarray,myarray+8,20);cout<<"num2:"<<num2<<endl;//通过谓词求vector大于3的个数int num3 = count_if(v.begin(),v.end(),IsGreat(3));cout<<"num3:"<<num3<<endl;//通过预定义函数对象 求大于3的个数/*//预定义函数对象greater 有两个参数  左参数来自容易的每一个元素 右参数通过bind2nd函数绑定2template <class T> struct greater : binary_function <T,T,bool> {bool operator() (const T& x, const T& y) const {return x>y;}};*/int num4 = count_if(v.begin(),v.end(),bind2nd(greater<int>(),2));cout<<"num4:"<<num4<<endl;//求奇数的个数 modulus/*//modulus 有两个参数 左操作数来自容器 右操作数来自bind2nd函数绑定的2template <class T> struct modulus : binary_function <T,T,T> {T operator() (const T& x, const T& y) const {return x%y;}};*/int num5 = count_if(v.begin(),v.end(),bind2nd(modulus<int>(),2));cout<<"num5:"<<num5<<endl;//求偶数的个数 modulusint num6 = count_if(v.begin(),v.end(),not1(bind2nd(modulus<int>(),2)));cout<<"num6:"<<num6<<endl;}int main(){display();system("pause");return 0;}
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