STL算法之accumulate函数学习

Accumulate函数学习、

头文件#include

当以迭代器first和last及值init作为参数调用时

accumulate(first,last, init);将把init 和从 first 到last 指向的值进行累加，并返回累加得到的和，但不包括last指向的值。通过实例学习accumulate 函数。

#include
#include
#include
using namespace std;
int main()
{
   cout<<"Demonstratint the accumulatefunction."<vectorl(&x[0],&x[5]);
   int sum = accumulate(vectorl.begin(),vectorl.end(),0);
cout<<"sum ="<#include
#include
#include
#include
using namespace std;
int mult(int x, int y)
{
   return x * y;
}
int main()
{
   int x[5] = {2, 3, 5, 7, 11};
   vectorvectorl(&x[0], &x[5]);
   int product = accumulate(vectorl.begin(), vectorl.end(), 1, mult);
   cout<<"product = "<





结果为

product = 2310

 

这里传递给accumulate 函数一个普通函数 mult ，实际上传递的是该函数的地址。

用multiplies 和 accumulate 求连乘

#include
#include
#include
#include
using namespace std;
int main()
{
   int x[5] = {2, 3, 5, 7, 11};
   vectorvectorl(&x[0], &x[5]);
   int product = accumulate(vectorl.begin(), vectorl.end(), 1,multiplies());
   cout<<"product = "<




结果为

product = 2310

通过multiplies() 调用了以int类型实例化的multiplies类的默认构造函数。

multiplies头文件为#include

一个实例在 http://www.linuxidc.com/Linux/2015-04/116423.htm 搬过来学习。

#include 
#include 
#include 
#include 
using namespace std;
int main( )
{
   vector  v1, v2( 20 );
   vector ::iterator Iter1, Iter2;


   int i;
   for ( i = 1 ; i < 21 ; i++ )
   {
      v1.push_back( i );
   }


   cout << "最初向量v1中个元素的值为:\n ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")." << endl;


   // accumulate函数的第一个功能，求和
   int total;
   total = accumulate ( v1.begin ( ) , v1.end ( ) , 0 );


   cout << "整数从1到20的和为: "
        << total << "." << endl;


   // 构造一个前n项和的向量
   int j = 0, partotal;
   for ( Iter1 = v1.begin( ) + 1; Iter1 != v1.end( ) + 1 ; Iter1++ )
   {
      partotal = accumulate ( v1.begin ( ) , Iter1 , 0 );
      v2 [ j ] = partotal;
      j++;
   }


   cout << "前n项和分别为:\n ( " ;
   for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
      cout << *Iter2 << " ";
   cout << ")." << endl << endl;


   // accumulate函数的第二个功能，计算连乘积
   vector  v3, v4( 10 );
   vector ::iterator Iter3, Iter4;


   int s;
   for ( s = 1 ; s < 11 ; s++ )
   {
      v3.push_back( s );
   }


   cout << "向量v3的初始值分别为:\n ( " ;
   for ( Iter3 = v3.begin( ) ; Iter3 != v3.end( ) ; Iter3++ )
      cout << *Iter3 << " ";
   cout << ")." << endl;


   int ptotal;
   ptotal = accumulate ( v3.begin ( ) , v3.end ( ) , 1 , multiplies( ) );


   cout << "整数1到10的连乘积为: "
        << ptotal << "." << endl;


   // 构造一个前n项积的向量
   int k = 0, ppartotal;
   for ( Iter3 = v3.begin( ) + 1; Iter3 != v3.end( ) + 1 ; Iter3++ ) {
      ppartotal = accumulate ( v3.begin ( ) , Iter3 , 1 , multiplies( ) );
      v4 [ k ] = ppartotal;
      k++;
   }


   cout << "前n项积分别为:\n ( " ;
   for ( Iter4 = v4.begin( ) ; Iter4 != v4.end( ) ; Iter4++ )
      cout << *Iter4 << " ";
   cout << ")." << endl;
}

刚开始学习STL，当做记笔记了！！！