我的函数中的百分比计算不起作用

Question

所以我想做的是获取一个数字向量，找出每个元素出现的次数，然后计算其在向量中出现的次数的等效百分比。

它在只有一个数字的几个元素的向量上工作得很好，但在多次出现不同元素（准确地说是 2 个）的向量上则完全没有。

这里有一个详细的输出：

count = 6
pushed back 21
total = 6
percent = 6 / 6* 100
pushed back 100
Number:
21 
Percent Chance
100 

count = 5
pushed back 42
count = 5
pushed back 21
total = 5
total = 10
percent = 5 / 10* 100
pushed back 0
percent = 5 / 10* 100
pushed back 0
Number:
42 
Percent Chance
0 // SHOULD BE 50
Number:
21 
Percent Chance
0 // SHOULD BE 50

代码如下：（输出来自此函数运行两次，使用不同的 x 向量）

 std::vector <std::string>  findpercentages(std::vector <std::string> x)
 {
 int count{};                          //for amount of times element occurs
 std::vector <std::string> tempvec{};  //to hold the element/s
 std::vector <int> counts{};           //to hold count for each element in tempvec
 std::vector <std::string> finalvec{}; //elements and counts of elements
 for (size_t i = 0; i < x.size(); i++)
 {
    //look for x[element] in tempvec, if not in tempvec, count occurances in x and add element to 
    // tempvec, add count to counts 
    std::vector <std::string>::iterator point { std::find(tempvec.begin(), tempvec.end(), x[i]) };
    if (point == tempvec.end())
    {
        count = std::count(x.begin(), x.end(), x[i]);
        std::cout << "count = " << count << '\n';
        counts.push_back(count);
        std::cout << "pushed back " << x[i] << '\n';
        tempvec.push_back(x[i]);

    }
}
int total{};
for (size_t n = 0; n < counts.size(); n++)
{
    total += counts[n]; //total for percentage calculation
    std::cout << "total = " << total << '\n';
}
for (size_t y = 0; y < tempvec.size(); y++)
{
    finalvec.push_back(tempvec[y]);
    //percent calculation. used unsigned_int64 because got arithmatic overflow warning if i just use 
    // int
    unsigned __int64 percentage = static_cast <unsigned __int64> (round((counts[y] / total) * 100));
    std::cout << "percent = " << counts[y] << " / " << total << "* 100" << '\n';
    finalvec.push_back(std::to_string(percentage));
    std::cout << "pushed back " << percentage << '\n';
}
return finalvec;
}

Answer 1

unsigned __int64 percentage = static_cast <unsigned __int64> (round((counts[y] / total) * 100));

应该是这样的

double percentage = round((100.0 * counts[y]) / total);

你的问题是，当你用一个整数除以另一个整数时，你总是得到一个整数。所以 (counts[y] / total) 总是 0 或 1.

所以最简单的解决办法就是在计算中引入一个double值100.0。这确保您得到浮点除法而不是整数除法。

我的函数中的百分比计算不起作用

percentage calculation in my function is not working

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percentage