Mixed Up Code Practice

We have a file called “locations.txt” that we want to read data from. Check to make sure that the file was opened properly; if it wasn’t, display an error message and exit with a status of 1. Put the necessary blocks of code in the correct order.

        int main() {
---
   ifstream infile("locations.txt");
---
   ifstream infile(locations.txt);  #paired
---
   if (infile.good() == false) {
---
   if (infile.good()) {  #paired
---
      cout << "Unable to open the file." << endl;
---
      exit(1);
---
      return 1;  #paired
---
   }
---
}
        

Let’s write a program that prompts the user for a filename and opens that file. Put the necessary blocks of code in the correct order.

        int main() {
---
   string filename;
---
   ifstream filename;  #paired
---
   cout << "Enter the name of the file: ";
---
   cin >> filename;
---
   ifstream infile(filename.c_str());
---
   ifstream infile(filename);  #paired
---
   if (infile.good() == false) {
---
      cout << "Unable to open the file." << endl;
---
      exit(1);
---
   }
---
}
        

Now let’s write some output to a file. Write a program that prompts a user for a list of 5 integers separated by spaces, calculates the average of those integers, and outputs “The average is average” to an output file called “average.txt”. Put the necessary blocks of code in the correct order. Declare the output file first and check that it is opened correctly.

        int main() {
---
   ofstream outfile("average.txt");
---
   if (outfile.good() == false) {
      cout << "Unable to open the file." << endl;
      exit(1);
   }
---
   vector list;  #distractor
---
   int sum = 0;
---
   int n1, n2, n3, n4, n5;
---
   cout << "Enter five integers separated by spaces: ";
---
   cin >> n1 >> n2 >> n3 >> n4 >> n5;
---
   sum = n1 + n2 + n3 + n4 + n5;
---
   outfile << "The average is " << sum / 5.0 << endl;
---
   cout << "The average is " << sum / 5.0 << endl;  #paired
---
}
        

We are given a file called “data.txt” with an unknown number of double values. Write a program that finds the minimum, maximum, and number of data and outputs these values to a file called “summary.txt”. Put the necessary blocks of code in the correct order. Declare the input and output files first, and check to see that both are opened correctly before dealing with data. Increment the number of data points before checking for the min and max.

        int main() {
---
   ifstream infile("data.txt");
---
   ofstream outfile("summary.txt");
---
   if (infile.good() == false || outfile.good() == false) {
      cout << "Unable to open a file." << endl;
      exit(1);
   }
---
   vector data;  #distractor
---
   int numData = 1;
---
   double min, max, value;
---
   infile >> value;
---
   min = value;
---
   max = value;
---
   while (infile >> value) {
---
      ++numData;
---
      if (value < min) { min = value; }
---
      if (value > max) { max = value; }
---
   }
---
   outfile << "Number of data: " << numData << ", min: " << min << ", max: " << max << endl;
---
}
        

You are given a file called “employee_data.txt” and you want to store the information from that file into a vector of data. The file contains information about an employee’s first and last name, age, phone number, and email. Write the definition of an Employee before you write your main function. Open and check the file before working with the data. Put the necessary blocks of code in the correct order.

        struct Employee {
   string fname;
   string lname;
   int age;
   int phone;
   string email;
---
   Employee(string f, string l, int a, int p, string e) {
      fname = f;
      lname = l;
      age = a;
      phone = p;
      email = e;
   }
---
};
---
int main() {
---
   ifstream infile("employee_data.txt");
---
   if (infile.good() == false) {
      cout << "Unable to open the file." << endl;
      exit(1);
   }
---
   vector data;
---
   string fname, lname, email;
---
   int age, phone;
---
   while (infile >> fname >> lname >> age >> phone >> email) {
---
   while (infile) {  #paired
---
      Employee e(fname, lname, age, phone, email);
---
      data.push_back(e);
---
   }
---
}
        

You are given a file but it appears that someone’s capslock key was stuck because everything is in uppercase. Write a program that takes the input from the file “UPPER.txt” and converts all the words to lowercase and prints out the modified message to a file called “lower.txt”. Write the definition of the function toLower first. Separate the words with spaces. Put the necessary blocks of code in the correct order.

        string upperToLower(string upper) {
   for (size_t i = 0; i < upper.length(); ++i) {
---
      upper[i] = toupper(upper[i]);
---
      tolower(upper[i]);  #paired
---
   }
   return upper;
}
---
int main() {
---
   ifstream infile("UPPER.txt");
---
   ofstream outfile("lower.txt");
---
   if (infile.good() == false || outfile.good() == false) {
      cout << "Unable to open a file." << endl;
      exit(1);
   }
---
   string word;
---
   while (infile >> word) {
---
      string upper = upperToLower(word);
---
      upperToLower(word);  #paired
---
      outfile << upper << " ";
---
   }
---
}
        

Nobody ever put a limit on how many files we can work with. Does this mean we can open two or more files at once? Yes we can! Write a program that combines two files “odds.txt” and “evens.txt” into one output file “numbers.txt”. You should combine them in a way such that “numbers.txt” contains the first odd number then the first even number then the second odd number and so on. You are guaranteed that there are equal amounts of odd and even numbers. Put the necessary blocks of code in the correct order.

        int main() {
---
   ifstream odds("odds.txt");
---
   ifstream evens("evens.txt");
---
   ofstream outfile("numbers.txt");
---
   if (!odds.good() || !evens.good() || !outfile.good()) {
      cout << "Unable to open a file." << endl;
      exit(1);
   }
---
   int odd, even;
---
   while (odds >> odd && evens >> even) {
---
      outfile << odd << " " << even << " ";
---
   }
---
}
        

In chapter 15.7 we defined the Set data structure. Write a function vectorToSet which takes a vector of data and returns a Set object with the data. Put the necessary blocks of code in the correct order. Put the Set definition first in your answer.

        class Set {
   private:
      vector elements;
      int numElements;

   public:
      Set (int n);

      int getNumElements () const;
      string getElement (int i) const;
      int find (const string& s) const;
      int add (const string& s);
};
---
Set vectorToSet(vector data) {
---
void Set::vectorToSet(vector data) {  #paired
---
   Set s(data.size());
---
   for (size_t i = 0; i < data.size(); ++i) {
---
      s.add(data[i]);
---
   }
---
   s.numElements++;  #distractor
---
   if (s.find(data[i]) != -1) {  #distractor
---
   s.elements.push_back(data[i]);  #distractor
---
}
        

Let’s write the struct definition for a Matrix! The underlying data structure is a vector of vectors of ints. Write the constructor and at function, which returns the data stored at a given row and column. Put the necessary blocks of code in the correct order.

        class Matrix {
---
   private:
---
      vector > elements;
---
   public:
---
      Matrix (int numRows, int numCols) {
---
         vector row(numCols);
---
         for (int i = 0; i < numRows; ++i) {
---
            elements.push_back(row);
---
         }
---
      }
---
      int at(int row, int col) {
---
         return elements[row][col];
---
      }
---
};
        

Now that we have the basic structure of a Matrix, let’s write a function that allows us to add data to a matrix. Write the Matrix member function setData which takes a row and column index as well as a data value and stores the data value in the Matrix at the given location. Then read data in from a file called data.txt. The first line contains the number of rows and columns, separated by a space. Data values begin on the next line. Put the necessary blocks of code in the correct order.

        void Matrix::setData (int row, int col, int value) {
---
void setData (int row, int col, int value) {  #paired
---
   elements[row][col] = value;
---
}
---
int main() {
---
   ifstream infile("data.txt");
---
   if (!odds.good() || !evens.good() || !outfile.good()) {
      cout << "Unable to open a file." << endl;
      exit(1);
   }
---
   int numRows, numCols, data;
---
   infile >> numRows >> numCols;
---
   Matrix mat(numRows, numCols);
---
   while (infile >> data) {
---
      for (int i = 0; i < numRows; ++i) {
---
         for (int j = 0; j < numCols; ++j) {
---
            mat.setData(i, j, data);
         }
      }
   }
---
}
        

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