c++ - 关于sstream，使用变量作为数组大小和计算溢出

需要从文本文件中读取一次而无需知道数组的大小，然后计算均值和方差。现在，我无法创建特定的数组。结果，我无法计算均值和方差。我真的希望你们能提供帮助。#include <iostream>#include <fstream>#include <string>#include <sstream>#include <math.h>#include "fraction.h"using namespace std;void ascending(fraction fractionarr[]);fraction mean(fraction fractionarr[]);fraction variance(fraction fractionarr[]);static const int countlinenumber(ifstream& data);void ascending(fraction fractionarr[]){ifstream data("data1.txt");fraction temp;fraction test(0, 1);int n = 0;int linenumber = countlinenumber(data);for (int i = 0; i < 100; i++){ if(fractionarr[i] != test) { n++; }}for (int i = 0; i < linenumber; i++){ for(int j = 0; j < linenumber-1; j++) { if(fractionarr[i+1] != test) { if(fractionarr[j] > fractionarr[j+1]) { temp = fractionarr[j]; fractionarr[j] = fractionarr[j+1]; fractionarr[j+1] = temp; } } }}}fraction mean(fraction fractionarr[]){ifstream data("data1.txt");fraction sum = fractionarr[0];fraction average;fraction n(1,1);fraction test(0,1);int linenumber = countlinenumber(data);for (int i = 1; i < linenumber; i++){ if(fractionarr[i] != test) { sum = sum + fractionarr[i]; n = n + fraction(1,1); }}average = sum / n;return average;}fraction variance(fraction fractionarr[]){ifstream data("data1.txt");fraction average = mean(fractionarr);fraction* semi = new fraction[100];fraction total;fraction t(1, 1);fraction variance;fraction test(0,1);int linenumber = countlinenumber(data);for (int i = 0; i < linenumber; i++){ if(fractionarr[i] != test) { semi[i] = (fractionarr[i]-average) * (fractionarr[i]-average); t = t + fraction(1, 1); }}total = semi[0];for (int i = 1; i < 100; i++){ if(semi[i] != test) { total = total + semi[i]; }}variance = total / t;return variance;}static const int countlinenumber(ifstream& data){string temp;int linenumber = 0;while(getline(data, temp) && !data.eof()){ linenumber++;}return linenumber;}int main(){ifstream data("data1.txt");ofstream data_out("data1_out.txt");stringstream ss;string temp;char op;fraction testing(0,1);fraction average;static const int linenumber = countlinenumber(data);int* numerator = new int[linenumber];int* denominator = new int[linenumber];fraction* fractionarr = new fraction[linenumber];for(int i = 0; i < linenumber; i++){ numerator[i] = 0; denominator[i] = 0;}for(int i = 0; i < linenumber; i++){ if(!data.eof()) { getline(data, temp, '\n'); ss << temp; ss >> numerator[i] >> op >> denominator[i]; ss.clear(); }}delete [] numerator;delete [] denominator;ascending(fractionarr);for (int i = 0; i < linenumber; i++){ if(fractionarr[i] != testing) data_out << fractionarr[i] << endl;}data_out.close();cout << mean(fractionarr) << endl;average = mean(fractionarr);cout << variance(fractionarr) << endl;system("pause");return 0;} 最佳答案 恐怕这看起来像是家庭作业，我被迫只提供一个方向的想法，而不是提供完整的解决方案来完成您所要求的一切。我希望这足以使您入门：#include <sstream>#include <vector>#include <iterator>#include <numeric>int main(){ std::istringstream input("1 200 50 9.5 300.1"); std::vector<double> numbers{std::istream_iterator<double>(input), std::istream_iterator<double>()}; double sum = std::accumulate(numbers.begin(), numbers.end(), 0.0); std::cout << "Sum: " << sum << "\n"; std::cout << "Count: " << numbers.size() << "\n";}这不会计算均值或方差，但是根据这里的内容，我相信添加均值的计算应该确实是微不足道的，并且方差仅稍微困难一点（请注意：对于方差，您需要使用lambda来计算均值的每个平方差）。