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15.9. A distance matrix¶

Finally, we are ready to put the data from the file into a matrix. Specifically, the matrix will have one row and one column for each city.

We’ll create the matrix in main, with plenty of space to spare:

matrix<int> distances (50, 50, 0);

Inside processLine, we add new information to the matrix by getting the indices of the two cities from the Set and using them as matrix indices:

int dist = convertToInt (distString);
int index1 = cities.add (city1);
int index2 = cities.add (city2);

distances[index1][index2] = distance;
distances[index2][index1] = distance;

Finally, in main we can print the information in a human-readable form:

for (int i=0; i<cities.getNumElements(); i++) {
  cout << cities.getElement(i) << "\t";

  for (int j=0; j<=i; j++) {
    cout << distances[i][j] << "\t";
  }
  cout << endl;
}

cout << "\t";
for (int i=0; i<cities.getNumElements(); i++) {
  cout << cities.getElement(i) << "\t";
}
cout << endl;

This code produces the output shown at the beginning of the chapter. The original data is available from this book’s web page.