STL中accumulate函数的使用

最新推荐文章于 2025-04-03 18:18:19 发布

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最新推荐文章于 2025-04-03 18:18:19 发布

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文章标签： vector iterator string float iostream c

本文通过一个具体的C++程序示例介绍了如何使用C++标准库中的组件进行数组操作，包括初始化、打印、求和及乘积计算，并展示了字符串数组的连接方法。

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#pragma warning (disable : 4786)

#include <iostream>
#include <numeric>
#include <functional>
#include <vector>
#include <iterator>
#include <string>

#if _MSC_VER > 1020 // if VC++ version is > 4.2
using namespace std; // std c++ libs implemented in std
#endif

typedef vector < float, allocator < float > > FloatArray;
typedef vector < string, allocator < string > > StringArray;
typedef ostream_iterator <float, char, char_traits <char> >
FloatOstreamIt;

void main ()
{
// a vector of floats
FloatArray rgFA;

// an ostream iterator that outputs a float to cout terminated
// by a space
FloatOstreamIt OstreamIt(cout," ");

// Initialize the array to 1,1/2,1/3,...
for (int i=0; i<10; i++) rgFA.push_back(1.0f/(i+1));

// Print the array
copy(rgFA.begin(),rgFA.end(),OstreamIt);
cout << endl;

// Sum the array
cout << "The sum of 1 + 1/2 + 1/3 + ... + 1/10 is "
<< accumulate(rgFA.begin(),rgFA.end(),0.0f)
<< endl;

// Compute the product of the array
cout << "The product of 1 * 1/2 * 1/3 * ... * 1/10 is "
<< accumulate(rgFA.begin(),rgFA.end(),1.0f,multiplies<float>())
<< endl;

// Initialize array of strings
StringArray rgs;
rgs.push_back("This ");
rgs.push_back("is ");
rgs.push_back("one ");
rgs.push_back("sentence. ");

// Concatenate the strings in the array & print the sentence
cout << "The concatenated vector of strings: "
<< accumulate(rgs.begin(),rgs.end(),string(""))
<< endl;
}

程序输出为：

1 0.5 0.333333 0.25 0.2 0.166667 0.142857 0.125 0.111111 0.1
The sum of 1 + 1/2 + 1/3 + ... + 1/10 is 2.92897
The product of 1 * 1/2 * 1/3 * ... * 1/10 is 2.75573e-007
The concatenated vector of strings: This is one sentence.

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