c++ 容器中元素计数
#include <iostream>
#include <algorithm>
#include <vector>
#include <functional>
#include<set>
using namespace std;
//一元谓词
bool isEven(int elementParam)
{
if (elementParam%2==0)
{
return true;
}
return false;
}
int main()
{
vector<int> vec1;
for (int k=0;k<10;k++)
{
vec1.push_back(k);
}
vec1.push_back(4);
vec1.push_back(4);
for (vector<int>::iterator iter=vec1.begin();iter !=vec1.end();++iter)
{
cout << *iter << " ";
}
cout << endl;
int num = count(vec1.begin(),vec1.end(),4);
cout << "" << num << endl;
//偶数的个数
int num2 = count_if(vec1.begin(),vec1.end(),isEven);
cout << "" << num2 << endl;
//bind2nd:函数适配器
//greater:函数对象 ,有两个参数,用于判断第一个参数是否大于第二个参数
int num3 = count_if(vec1.begin(),vec1.end(),bind2nd(greater<int>(),6));
cout << "大于4的数:"<<num3<< endl;
int num4 = count_if(vec1.begin(),vec1.end(),bind2nd(modulus<int>(),2));
cout << "偶数个数:" << num4 << endl;
multiset<int> multiset1;
for (int k=0;k<10;k++)
{
multiset1.insert(multiset1.begin(),k);
}
multiset1.insert(3);
multiset1.insert(6);
multiset1.insert(6);
multiset<int>::iterator multiset_iter1;
for (multiset_iter1 = multiset1.begin();multiset_iter1 !=multiset1.end();++multiset_iter1)
{
cout << *multiset_iter1 << " ";
}
cout << endl;
int num5 = count(multiset1.begin(),multiset1.end(),3);
cout << "count:" << num5 << endl;
//效率高
int num6 = multiset1.count(6);
cout << "count:" << num6 << endl;
system("pause");
return 0;
}
===================================================
0 1 2 3 4 5 6 7 8 9 4 4
3
7
大于4的数:3
偶数个数:5
0 1 2 3 3 4 5 6 6 6 7 8 9
count:2
count:3
请按任意键继续. . .