vector所有元素相加求和_利用accumulate函数

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自己使用时的两行代码

#include<numeric>  //使用accumulate函数要包含这个头文件vector<float> result = {1.2， 2.3， 3.4};
float scoreSum = accumulate(result.begin(), result.end(), 0.0);

然后看一下http://www.cplusplus.com/reference/上面关于accumulate的介绍

函数原型：

sum (1)	
template <class InputIterator, class T>T accumulate (InputIterator first, InputIterator last, T init);
custom (2)	
template <class InputIterator, class T, class BinaryOperation>T accumulate (InputIterator first, InputIterator last, T init,BinaryOperation binary_op);

template <class InputIterator, class T>T accumulate (InputIterator first, InputIterator last, T init)
{while (first!=last) {init = init + *first;  // or: init=binary_op(init,*first) for the binary_op version++first;}return init;
}

示例： 

// accumulate example
#include <iostream>     // std::cout
#include <functional>   // std::minus
#include <numeric>      // std::accumulateint myfunction (int x, int y) {return x+2*y;}
struct myclass {int operator()(int x, int y) {return x+3*y;}
} myobject;int main () {int init = 100;int numbers[] = {10,20,30};std::cout << "using default accumulate: ";std::cout << std::accumulate(numbers,numbers+3,init);std::cout << '\n';std::cout << "using functional's minus: ";std::cout << std::accumulate (numbers, numbers+3, init, std::minus<int>());std::cout << '\n';std::cout << "using custom function: ";std::cout << std::accumulate (numbers, numbers+3, init, myfunction);std::cout << '\n';std::cout << "using custom object: ";std::cout << std::accumulate (numbers, numbers+3, init, myobject);std::cout << '\n';return 0;
}

输出结果：

using default accumulate: 160
using functional's minus: 40
using custom function: 220
using custom object: 280

 

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