C++ STL算法系列1---count函数

cout<<count(ivec.begin() , ivec.end() , searchValue)

 1 //读取一系列int数据，并将它们存储到vector对象中，
 2 //然后使用algorithm头文件中定义的名为count的函数，
 3 //统计某个指定的值出现了多少次
 4 #include<iostream>
 5 #include<vector>
 6 #include<algorithm>
 7 using namespace std;
 8  
 9 int main()
10 {
11     int ival , searchValue;
12     vector<int> ivec;
13  
14     //读入int型数据并存储到vector对象中，直至遇到文件结束符
15     cout<<"Enter some integers(Ctrl+Z to end): "<<endl;
16     while(cin >> ival)
17         ivec.push_back(ival);
18  
19     cin.clear(); // 使输入流重新有效
20  
21     //读入欲统计其出现次数的int值
22     cout<<"Enter an integer you want to search: "<<endl;
23     cin>>searchValue;
24  
25     //使用count函数统计该值出现的次数并输出结果
26     cout<<count(ivec.begin() , ivec.end() , searchValue)
27         <<"  elements in the vector have value "
28         <<searchValue<<endl;
29  
30     return 0;
31 }

 1 #include <vector>
 2 #include <algorithm>
 3 #include <iostream>
 4 
 5 bool greater10(int value)
 6 {
 7     return value >10;
 8 }
 9 
10 int main()
11 {
12     using namespace std;
13     vector<int> v1;
14     vector<int>::iterator Iter;
15 
16     v1.push_back(10);
17     v1.push_back(20);
18     v1.push_back(10);
19     v1.push_back(40);
20     v1.push_back(10);
21 
22     cout << "v1 : ";
23     for (Iter = v1.begin(); Iter != v1.end(); Iter++)
24        cout << *Iter << " ";
25     cout << endl;
26 
27 
28     vector<int>::size_type  result1 = count_if(v1.begin(), v1.end(), greater10);  //count_if算法返回使谓词函数返回条件成立的元素个数
29     cout << "The number of elements in v1 greater than 10 is: "
30          << result1 << "." << endl;
31 
32     return 0;
33 }

count       ：  在序列中统计某个值出现的次数

count_if   :    在序列中统计与某谓词匹配的次数