Project 1 Step 1 hints and solutions check

Author: kcpearce

Project#01/hints/hint1-1.md

@@ -1,4 +1,3 @@
-## Hint 1-1: Opening and closing the file stream
 To open a file named "geom.dat", you need a file stream object:
 
 ```c++
@@ -10,12 +9,12 @@ To open a file named "geom.dat", you need a file stream object:
 
 int main()
 {  
-    ifstream input("geom.dat");
+  ifstream input("geom.dat");
 
-    ...
+  ...
 
-    input.close();
+  input.close();
 
-    return 0;
+  return 0;
 }
 ```

Project#01/hints/hint1-2.md

@@ -0,0 +1,21 @@
+Use the ">>" operator to read the data from the file:
+
+```c++
+#include <iostream>
+#include <fstream>
+#include <iomanip>
+
+...
+
+int main()
+{  
+  ifstream input("geom.dat");
+
+  int natom;
+  input >> natom;
+    
+  input.close();
+
+  return 0;
+}
+```

Project#01/hints/hint1-3.md

@@ -0,0 +1,37 @@
+It may be convenient to use arrays to store the z-values and Cartesian coordinates of the atoms:
+```c++
+int zval[50];
+double x[50], y[50], z[50]; 
+```
+
+A more elegant solution is to allocate the memory dynamically for each array once you know the number of atoms:
+```c++
+#include <iostream>
+#include <fstream>
+#include <iomanip>
+
+...
+
+int main()
+{  
+  ifstream input("geom.dat");
+
+  int natom;
+  input >> natom;
+
+  input.close();
+  
+  int *zval = new int[natom];
+  double *x = new double[natom];
+  double *y = new double[natom];
+  double *z = new double[natom];
+
+  ...
+
+  delete[] zval;  delete[] x;  delete[] y;  delete[] z;
+
+  return 0;
+}
+```
+
+Don't forget to delete[] the memory after you're finished!

Project#01/hints/step1-solution.md

@@ -0,0 +1,60 @@
+```c++
+#include <iostream>
+#include <fstream>
+#include <iomanip>
+#include <cstdio>
+
+using namespace std;
+
+int main()
+{
+  ifstream input("geom.dat");
+
+  int natom;
+  input >> natom;
+
+  int *zval = new int[natom];
+  double *x = new double[natom];
+  double *y = new double[natom];
+  double *z = new double[natom];
+
+  for(int i=0; i < natom; i++)
+    input >> zval[i] >> x[i] >> y[i] >> z[i];
+ 
+  input.close();
+
+  cout << "Number of atoms: " << natom << endl;
+  cout << "Input Cartesian coordinates:\n";
+  for(int i=0; i < natom; i++)
+    printf("%d %20.12f %20.12f %20.12f\n", (int) zval[i], x[i], y[i], z[i]);
+
+  delete[] zval;
+  delete[] x;  delete[] y;  delete[] z;
+
+  return 0;
+}
+```
+
+An even more elegant solution would be to couple the above to the [Molecule class](https://github.com/CrawfordGroup/ProgrammingProjects/wiki/Classes-and-Objects) we defined earlier in the Fundamentals section:
+```c++
+#include "molecule.h"
+#include <iostream>
+#include <fstream>
+#include <iomanip>
+#include <cstdio>
+
+using namespace std;
+
+int main()
+{
+  Molecule mol("geom.dat", 0);
+
+  cout << "Number of atoms: " << mol.natom << endl;
+  cout << "Input Cartesian coordinates:\n";
+  mol.print_geom();
+
+  return 0;
+}
+```
+
+