1. 介紹
用來計算特定范圍內（包括連續的部分和初始值）所有元素的和，除此之外，還可以用指定的二進制操作來計算特定范圍內的元素結果。其頭文件在numeric中。
用次函數可以求和，構造前n項和的向量，乘積，構造前n項乘積的向量
2. 應用舉例
#include <vector> #include <numeric> #include <functional> #include <iostream> using namespace std; int main( ) { vector <int> v1, v2( 20 ); vector <int>::iterator Iter1, Iter2; int i; for ( i = 1 ; i < 21 ; i++ ) { v1.push_back( i ); } cout << "最初向量v1中個元素的值為:\n ( " ; for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ ) cout << *Iter1 << " "; cout << ")." << endl; // accumulate函數的第一個功能，求和 int total; total = accumulate ( v1.begin ( ) , v1.end ( ) , 0 ); cout << "整數從1到20的和為: " << total << "." << endl; // 構造一個前n項和的向量 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項和分別為:\n ( " ; for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ ) cout << *Iter2 << " "; cout << ")." << endl << endl; // accumulate函數的第二個功能，計算連乘積 vector <int> v3, v4( 10 ); vector <int>::iterator Iter3, Iter4; int s; for ( s = 1 ; s < 11 ; s++ ) { v3.push_back( s ); } cout << "向量v3的初始值分別為:\n ( " ; for ( Iter3 = v3.begin( ) ; Iter3 != v3.end( ) ; Iter3++ ) cout << *Iter3 << " "; cout << ")." << endl; int ptotal; ptotal = accumulate ( v3.begin ( ) , v3.end ( ) , 1 , multiplies<int>( ) ); cout << "整數1到10的連乘積為: " << ptotal << "." << endl; // 構造一個前n項積的向量 int k = 0, ppartotal; for ( Iter3 = v3.begin( ) + 1; Iter3 != v3.end( ) + 1 ; Iter3++ ) { ppartotal = accumulate ( v3.begin ( ) , Iter3 , 1 , multiplies<int>( ) ); v4 [ k ] = ppartotal; k++; } cout << "前n項積分別為:\n ( " ; for ( Iter4 = v4.begin( ) ; Iter4 != v4.end( ) ; Iter4++ ) cout << *Iter4 << " "; cout << ")." << endl; }
編譯運行，看一下輸出結果： 