阅读矩阵txt文件并存储为数组

Question

我目前正在编写一个模拟退火代码来解决旅行商问题，并遇到了存储和使用从txt文件中读取数据的困难。文件中的每一行&列表示各城市，存储为15×15矩阵的两个不同城市之间的距离：

0.0 5.0 5.0 6.0 7.0 2.0 5.0 2.0 1.0 5.0 5.0 1.0 2.0 7.1 5.0 
5.0 0.0 5.0 5.0 5.0 2.0 5.0 1.0 5.0 6.0 6.0 6.0 6.0 1.0 7.1 
5.0 5.0 0.0 6.0 1.0 6.0 5.0 5.0 1.0 6.0 5.0 7.0 1.0 5.0 6.0 
6.0 5.0 6.0 0.0 5.0 2.0 1.0 6.0 5.0 6.0 2.0 1.0 2.0 1.0 5.0 
7.0 5.0 1.0 5.0 0.0 7.0 1.0 1.0 2.0 1.0 5.0 6.0 2.0 2.0 5.0 
2.0 2.0 6.0 2.0 7.0 0.0 5.0 5.0 6.0 5.0 2.0 5.0 1.0 2.0 5.0 
5.0 5.0 5.0 1.0 1.0 5.0 0.0 2.0 6.0 1.0 5.0 7.0 5.0 1.0 6.0 
2.0 1.0 5.0 6.0 1.0 5.0 2.0 0.0 7.0 6.0 2.0 1.0 1.0 5.0 2.0 
1.0 5.0 1.0 5.0 2.0 6.0 6.0 7.0 0.0 5.0 5.0 5.0 1.0 6.0 6.0 
5.0 6.0 6.0 6.0 1.0 5.0 1.0 6.0 5.0 0.0 7.0 1.0 2.0 5.0 2.0 
5.0 6.0 5.0 2.0 5.0 2.0 5.0 2.0 5.0 7.0 0.0 2.0 1.0 2.0 1.0 
1.0 6.0 7.0 1.0 6.0 5.0 7.0 1.0 5.0 1.0 2.0 0.0 5.0 6.0 5.0 
2.0 6.0 1.0 2.0 2.0 1.0 5.0 1.0 1.0 2.0 1.0 5.0 0.0 7.0 6.0 
7.0 1.0 5.0 1.0 2.0 2.0 1.0 5.0 6.0 5.0 2.0 6.0 7.0 0.0 5.0 
5.0 7.0 6.0 5.0 5.0 5.0 6.0 2.0 6.0 2.0 1.0 5.0 6.0 5.0 0.0 

要阅读此我有一个LoadCities（）函数，如下所示：

#include "iostream" 
#include "fstream"  
#include "string" 
using namespace std; 

double distances [15][15]; 

void LoadCities() 
{ 
    ifstream CityFile; 

    if (!CityFile.is_open()) //check is file has been opened 
    { 
     CityFile.open ("Cities.txt", ios::in | ios::out); 

     if (!CityFile) 
     { 
      cerr << "Failed to open " << CityFile << endl; 
      exit(EXIT_FAILURE); //abort program 
     } 
    } 

    int length; 
    char * buffer; 
    string cities; 

    CityFile.seekg(0, ios::end); 
    length = CityFile.tellg(); 
    CityFile.seekg (0, ios::beg); 

    buffer = new char [length]; 

    cities = CityFile.read (buffer,length); 

    string rows = strtok(cities, "\n"); 

    distances = new double[rows.length()][rows.length()]; 

      for (int i = 0; i < (string) rows.length(); i++) 
      { 
       string distance = strtok(rows[i], " "); 

       for (int j = 0; j < distance.length(); j++) 
       { 
        distances[i][j] = (double) Parse(distance[j]); 
       } 
      } 

    CityFile.close(); 
} 

我已经尝试另一种istreambuf_iterator方法去操纵读材料到阵列的点，但是我似乎总是遇到的并发症：

ifstream CityFile("Cities.txt"); 
string theString((std::istreambuf_iterator<char>(CityFile)), std::istreambuf_iterator<char>()); 

任何帮助都会很受欢迎。一直没有成功的抨击我的头！

################编辑/更新

@ SoapBox - 一些SA代码，函数和main（）的细节。这不是干净，高效，整洁，并不是要在这个阶段，只需要工作的时刻。该版本（如下）可用于解决多项式问题（最简单的问题）。有什么需要做的将其转换为一个旅行商问题是：

1. 写LoadCities（）函数来收集距离数据。 （电流）

2. 更改初始化（）来获得距离的总参与

3. 变化E（）的TSP功能（例如，计算得到随机路线的距离）

的后两个我知道我可以做，但我需要LoadCities（）来做到这一点。以下脚本中没有其他内容需要更改。

#include "math.h" 
#include "iostream" 
#include "fstream" 
#include "time.h" // Define time() 
#include "stdio.h" // Define printf() 
#include "randomc.h" // Define classes for random number generators 
#include "mersenne.cpp" // Include code for the chosen random number generator 

using namespace std; // For the use of text generation in application 

double T; 
double T_initial; 

double S; 
double S_initial; 
double S_current; 
double S_trial; 

double E_current; 

int N_step;  // Number of Iterations for State Search per Temperature 
int N_max;   //Number of Iterations for Temperature 
int Write; 

const double EXP = 2.718281828; 

//------------------------------------------------------------------------------ 
//Problem Function of Primary Variable (Debugged 17/02/09 - Works as intended) 

double E(double x) //ORIGNINAL 
{ 
    double y = x*x - 6*x + 2; 

    return y; 
} 

//------------------------------------------------------------------------------ 
//Random Number Generation Function (Mod 19/02/09 - Generated integers only & fixed sequence) 

double Random_Number_Generator(double nHigh, double nLow) 
{ 
    int seed = (int)time(0);   // Random seed 

    CRandomMersenne RanGen(seed);  // Make instance of random number generator 

    double fr;       // Random floating point number 

    fr = ((RanGen.Random() * (nHigh - nLow)) + nLow); // Generatres Random Interger between nLow & nHigh 

    return fr; 
} 

//------------------------------------------------------------------------------ 
//Initializing Function (Temp 17/02/09) 

void Initialize() //E.g. Getting total Distance between Cities 
{ 
    S_initial = Random_Number_Generator(10, -10); 

    cout << "S_Initial: " << S_initial << endl; 
} 

//------------------------------------------------------------------------------ 
//Cooling Schedule Function (make variables) (Completed 16/02/09) 

double Schedule(double Temp, int i) // Need to find cooling schedule 
{ 
    double CoolingRate = 0.9999; 

    return Temp *= CoolingRate; 
} 

//------------------------------------------------------------------------------ 
//Next State Function (Mod 18/02/09) 

double Next_State(double T_current, int i) 
{ 
     S_trial = Random_Number_Generator(pow(3, 0.5), pow(3, 0.5)*-1); 

     S_trial += S_current; 

     double E_t = E(S_trial); 
     double E_c = E(S_current); 

     double deltaE = E_t - E_c;        //Defines gradient of movement 

     if (deltaE <= 0)          //Downhill 
     {  
      S_current = S_trial; 
      E_current = E_t; 
     } 
     else             //Uphill 
     { 
      double R = Random_Number_Generator(1,0);   //pseudo random number generated 
      double Ratio = 1-(float)i/(float)N_max;    //Control Parameter Convergence to 0 
      double ctrl_pram = pow(EXP, (-deltaE/T_current)); //Control Parameter 

      if (R < ctrl_pram*Ratio)       //Checking 
      { 
       S_current = S_trial;       //Expresses probability of uphill acceptance 
       E_current = E_t;         
      } 
      else 
       E_current = E_c; 
     } 

     return S_current; 
} 

//------------------------------------------------------------------------------ 
//Metropolis Function (Mod 18/02/09) 

double Metropolis(double S_start, double T_current, int N_Steps, int N_temperatures) 
{ 
    S_current = S_start;          //Initialised S_initial equated to S_current 

    for (int i=1; i <= N_step; i++)       //Iteration of neighbour states 
     S_current = Next_State(T_current, N_temperatures);  //Determines acceptance of new states 

    return S_current; 
} 

//------------------------------------------------------------------------------ 
//Write Results to Notepad (Completed 18/02/09) 

void WriteResults(double i, double T, double x, double y) 
{ 
//This function opens a results file (if not already opened) 
//and stores results for one time step 

    static ofstream OutputFile; 
    const int MAXLENGTH = 80; 

    if (!OutputFile.is_open()) //check is file has been opened 
    { 
     //no it hasn't. Get a file name and open it. 
     char FileName[MAXLENGTH]; 

     //read file name 
     cout << "Enter file name: "; 
     do 
     { 
      cin.getline(FileName, MAXLENGTH); 
     } 
     while (strlen(FileName) <= 0); //try again if length of string is 0 

     //open file 
     OutputFile.open(FileName); 

     // check if file was opened successfully 
     if (!OutputFile) 
     { 
      cerr << "Failed to open " << FileName << endl; 
      exit(EXIT_FAILURE); //abort program 
     } 

     OutputFile << "Iterations" << '\t' << "Temperatures" << '\t' << "X-Value" << '\t' << "Y-Value" << endl; 
     OutputFile << endl; 
    } 

    //OutputFile.width(10); 
    OutputFile << i << '\t' << T << '\t' << x << '\t' << y << endl; 

    if (i == N_max) 
    { 
     OutputFile << endl 
       << "Settings: " << endl 
       << "Initial Temperature: " << T_initial << endl 
       << "Temperature Iterations: " << N_max << endl 
       << "Step Iterations: " << N_step << endl 
       << endl 
       << "Results: " << endl 
       << "Final Temperature: " << T << endl 
       << "Minimum: " << S << endl; 

     OutputFile.close(); 
    } 
} 

//------------------------------------------------------------------------------ 
//Main SA Function (Mod 17/02/09) 

void SA(int W) 
{ 
    S = S_initial; 
    T = T_initial; 

    for (int N_temperatures = 1 ; N_temperatures <= N_max ; N_temperatures++) 
    { 
     S = Metropolis(S, T, N_step, N_temperatures); 
     T = Schedule(T, N_temperatures); 

     if (W == 1) 
      WriteResults(N_temperatures, T, S, E_current); 
    } 

    cout << "Result" << endl 
    << "Y-value> " << S << endl 
    << "Temperature> " << T << endl; 

} 

//------------------------------------------------------------------------------ 
//Execution of Traveling Salesman Problem (Progress 18/02/09) 


int main() 
{ 
    cout << "Quadratic Function" << endl 
     << "Solving method: Simulated Annealing" << endl; 
    cout << "" << endl; 

    cout << "Select desired Initial Temperature:" << endl 
     << "> "; 
    cin >> T_initial; 

    cout << "Select desired number of Temperature Iterations:" << endl 
     << "> "; 
    cin >> N_max; 

    cout << "Select desired number of step Iterations:" << endl 
     << "> "; 
    cin >> N_step; 

    Initialize(); 

    cout << "Write to file: (1/0) " << endl 
     << "> "; 
    cin >> Write; 

    SA(Write); 

    system ("PAUSE"); 

    return 0; 
} 

@ strager - 我知道它不好的代码，但不幸的是与参与我的项目的时间限制和consiquental学习曲线，结果是需要什么样的！ :)它将在后期整理。

@ dirkgently - 这是这样做的最初原因，因此我的第一次尝试就是这样去做。

Answer 1

这个怎么样？（KISS解决方案）

void LoadCities() { 
    int x, y; 
    ifstream in("Cities.txt"); 

    if (!in) { 
    cout << "Cannot open file.\n"; 
    return; 
    } 

    for (y = 0; y < 15; y++) { 
    for (x = 0; x < 15; x++) { 
     in >> distances[x][y]; 
    } 
    } 

    in.close(); 
} 

适合我。可能不是那么复杂，也许不是很高效，但只要你不读1000x1000阵列，你就不会看到任何区别。

Answer 2

它甚至编译？我得到〜7个错误。样品：

strtok(cities, "\n");

strtok()第一个参数是一个char *，而不是一个std ::字符串。

这有帮助吗？

void LoadCities() 
{ 
    std::vector<double> f((std::istream_iterator<double> 
     (std::ifstream("city.txt"))), /* replace filename with your own */ 
    (std::istream_iterator<double>())); 
    if (!f.empty()) { 
    std::cout << f.size() << "\n"; 
    /* print an arbitrary data point with 2 places of decimal */ 
    std::cout << std::setprecision(2) << f[ 0 ] << std::endl; 

    } 
} 

使用矩阵并不意味着您需要有一个多维数组。尤其是2D数组。当然它更容易读写;）

Answer 3

你可能想简单的东西，像这样：

std::vector<std::vector<std::string> > LoadCities(const std::string &filename) 
{ 
    using namespace std; 

    ifstream file; 
    file.open(filename, ios::in | ios::out); 

    if(!file.is_open()) { 
     // error 
     return vector<vector<double> >(); 
    } 

    vector<vector<double> > data; 
    string line; 

    while(!std::getline(file, line, '\n').eof()) { 
     istringstream reader(line); 

     vector<double> lineData; 

     string::const_iterator i = line.begin(); 

     while(!reader.eof()) { 
      double val; 
      reader << val; 

      if(reader.fail()) 
       break; 

      lineData.push_back(val); 
     } 

     data.push_back(lineData); 
    } 

    return data; 
} 

基本上你使用流输入数据。我可能做错了事（我从来没有处理过iostreams; P），但是这应该给你关于如何构造矩阵读取器的一般想法。

Answer 4

这是我如何将加载/保存：

#include <iostream> 
#include <fstream> 
#include <string> 

int width = 0; 
int height = 0; 
double **distances; 

void WriteDouble(std::ofstream &stream, double toWrite) 
{ 
    char buffer[8]; 
    memcpy(buffer, &toWrite, 8); 
    stream.write(buffer, 8); 
} 

void WriteInt(std::ofstream &stream, int toWrite) 
{ 
    char buffer[4]; 
    memcpy(buffer, &toWrite, 4); 
    stream.write(buffer, 4); 
} 

double ReadDouble(std::ifstream &stream) 
{ 
    double d = 0; 
    stream.read((char *)&d, 8); 
    return d; 
} 

int ReadInt(std::ifstream &stream) 
{ 
    int i = 0; 
    stream.read((char *)&i, 4); 
    return i; 
} 

void Save() 
{ 
    std::ofstream stream("cities", std::ios::out | std::ios::binary); 

    if(!stream.good()) { 
     throw std::exception("Error opening stream"); 
    } 

    WriteInt(stream, width); 
    WriteInt(stream, height); 

    for(int x = 0; x < width; x++) { 
     for(int y = 0; y < height; y++) { 
      WriteDouble(stream, distances[x][y]); 
     } 
    } 

    stream.close(); 
} 

void Load() 
{ 
    std::ifstream stream("cities", std::ios::in | std::ios::binary); 

    if(!stream.good()) { 
     throw std::exception("Error opening stream"); 
    } 

    width = ReadInt(stream); 
    height = ReadInt(stream); 

    distances = new double *[width]; 

    for(int i = 0; i < width; i++) { 
     distances[i] = new double[height]; 
    } 

    for(int x = 0; x < width; x++) { 
     for(int y = 0; y < height; y++) { 
      distances[x][y] = ReadDouble(stream); 
     } 
    } 

    stream.close(); 
} 

void RunSaveTest() 
{ 
    width = 15; 
    height = 15; 

    distances = new double *[width]; 

    for(int i = 0; i < width; i++) { 
     distances[i] = new double[height]; 
    } 

    for(int x = 0; x < width; x++) { 
     for(int y = 0; y < height; y++) { 
      distances[x][y] = (double)x/(double)(y + 1); 
      std::cout << distances[x][y] << std::endl; 
     } 
    } 

    Save(); 
} 

void RunLoadTest() 
{ 
    Load(); 

    for(int x = 0; x < width; x++) { 
     for(int y = 0; y < height; y++) { 
      std::cout << distances[x][y] << std::endl; 
     } 
    } 
} 

int main() 
{ 
    RunSaveTest(); 
    // RunLoadTest(); 

    return 0; 
} 

Answer 5

参考从我的博客：http://www.topbug.net/blog/2013/01/10/load-a-matrix-from-an-ascii-format-file/

此代码段中，而不是假设一切都很好格式化更高的容错能力。

#include <istream> 
#include <string> 
#include <sstream> 
#include <vector> 

// load matrix from an ascii text file. 
void load_matrix(std::istream* is, 
     std::vector< std::vector<double> >* matrix, 
     const std::string& delim = " \t") 
{ 
    using namespace std; 

    string  line; 
    string  strnum; 

    // clear first 
    matrix->clear(); 

    // parse line by line 
    while (getline(*is, line)) 
    { 
     matrix->push_back(vector<double>()); 

     for (string::const_iterator i = line.begin(); i != line.end(); ++ i) 
     { 
      // If i is not a delim, then append it to strnum 
      if (delim.find(*i) == string::npos) 
      { 
       strnum += *i; 
       if (i + 1 != line.end()) // If it's the last char, do not continue 
        continue; 
      } 

      // if strnum is still empty, it means the previous char is also a 
      // delim (several delims appear together). Ignore this char. 
      if (strnum.empty()) 
       continue; 

      // If we reach here, we got a number. Convert it to double. 
      double  number; 

      istringstream(strnum) >> number; 
      matrix->back().push_back(number); 

      strnum.clear(); 
     } 
    } 
} 

// example 
#include <fstream> 
#include <iostream> 

int main() 
{ 
    using namespace std; 

    // read the file 
    std::ifstream is("input.txt"); 

    // load the matrix 
    std::vector< std::vector<double> > matrix; 
    load_matrix(&is, &matrix); 

    // print out the matrix 
    cout << "The matrix is:" << endl; 
    for (std::vector< std::vector<double> >::const_iterator it = matrix.begin(); it != matrix.end(); ++ it) 
    { 
     for (std::vector<double>::const_iterator itit = it->begin(); itit != it->end(); ++ itit) 
      cout << *itit << '\t'; 

     cout << endl; 
    } 

    return 0; 
}