Daily Archives: February 12, 2012
C++ || Snippet – How To Read & Write Data From A File
This page will consist of a demonstration of a simple quadratic formula program, which highlights the use of the input/output mechanisms of manipulating a text file. This program will read in data from a file (numbers), manipulate that data, and output new data into a different text file.
REQUIRED KNOWLEDGE FOR THIS SNIPPET
NOTE: The data file that is used in this example can be downloaded here.
Also, in order to read in the data .txt file, you need to save the .txt file in the same directory (or folder) as your .cpp file is saved in. If you are using Visual C++, this directory will be located in
Documents > Visual Studio > Projects > [Your project name] > [Your project name]
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 |
// ============================================================================ // Author: Kenneth Perkins // Date: Feb 12, 2012 // Taken From: http://programmingnotes.org/ // File: FileInput.cpp // Description: Demonstrates how to read data from a file // ============================================================================ #include <iostream> #include <fstream> #include <cstdlib> // used for the 'exit' command #include <cmath> using namespace std; int main () { // declare variables ifstream infile; ofstream outfile; double a=0,b=0,c=0; double root1=0, root2=0; // this opens the input file // YOUR INPUT FILE NAME GOES BELOW infile.open("INPUT_Quadratic_programmingnotes_freeweq_com.txt"); // check to see if the file even exists, & if not then EXIT if(infile.fail()) { cout<<"\nError, the input file could not be found!\n"; exit(1); // exits the program } // this opens the output file // if the file doesnt already exist, it will be created outfile.open("OUTPUT_Quadratic_programmingnotes_freeweq_com.txt"); // this loop reads in data until there is no more // data contained in the file while(infile.good()) { // this assigns the incoming data to the // variables 'a', 'b' and 'c' // NOTE: it is just like a cin >> statement infile >> a >> b >> c; // NOTE: if you want to read in data into an array // your declaration would be like this // ------------------------------------ // infile >> a[counter] >> b[counter] >> c[counter]; // ++counter; } // this does the quadratic formula calculations root1 = ((-b) + sqrt(pow(b,2) - (4*a*c)))/(2*a); root2 = ((-b) - sqrt(pow(b,2) - (4*a*c)))/(2*a); // this displays the numbers to screen via cout cout <<"For the numbers\na = "<<a<<"\nb = "<<b<<"\nc = "<<c<<endl; cout <<"\nroot 1 = "<<root1<<"\nroot 2 = "<<root2<<endl; // this saves the data to the output file // NOTE: its almost exactly the same as the cout statement outfile <<"For the numbers\na = "<<a<<"\nb = "<<b<<"\nc = "<<c<<endl; outfile <<"\nroot 1 = "<<root1<<"\nroot 2 = "<<root2<<endl; // close the input/output files once you are done using them infile.close(); outfile.close(); // stops the program from automatically closing cin.get(); return 0; }// http://programmingnotes.org/ |
QUICK NOTES:
The highlighted lines are sections of interest to look out for.
The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.
Once compiled, you should get this as your output
For the numbers
a = 2
b = 4
c = -16root 1 = 2
root 2 = -4
C++ || Snippet – How To Find The Highest & Lowest Numbers Contained In An Integer Array
This page will consist of a simple demonstration for finding the highest and lowest numbers contained in an integer array.
REQUIRED KNOWLEDGE FOR THIS SNIPPET
Finding the highest/lowest values in an array can be found in one or two ways. The first way would be via a sort, which would render the highest/lowest numbers contained in the array because the values would be sorted in order from highest to lowest. But a sort may not always be practical, especially when you want to keep the array values in the same order that they originally came in.
The second method of finding the highest/lowest values is by traversing through the array, checking each value it contains one by one to determine if the current number which is being compared truly is a target value or not. That method will be displayed below.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 |
// ============================================================================ // Author: Kenneth Perkins // Date: Feb 12, 2012 // Taken From: http://programmingnotes.org/ // File: arrayMinMax.cpp // Description: Determines the highest and lowest value in an array // ============================================================================ #include <iostream> #include <iomanip> #include <ctime> using namespace std; const int NUM_INTS = 14; int main() { // declare variables int arry[NUM_INTS]; // array is initialized using a const variable srand(time(NULL)); // place random numbers into the array for (int x = 0; x < NUM_INTS; ++x) { arry[x] = rand() % 100 + 1; } cout << "Original array values" << endl; // Output the original array values for (int x = 0; x < NUM_INTS; ++x) { cout << setw(4) << arry[x]; } // creates a line separator cout << "\n--------------------------------------------------------"; // use a for loop to go thru the array checking to see the highest/lowest element cout << "\nThese are the highest and lowest array values: "; // set the lowest/highest to the first array item (if any) int lowestScore = NUM_INTS > 0 ? arry[0] : 0; int highestScore = lowestScore; for (int index = 1; index < NUM_INTS; ++index) { // if current score in the array is bigger than the current 'highestScore' // element, then set 'highestScore' equal to the current array element if (arry[index] > highestScore) { highestScore = arry[index]; } // if current score in the array is smaller than the current 'lowestScore' // element, then set 'lowestScore' equal to the current array element if (arry[index] < lowestScore) { lowestScore = arry[index]; } }// end for loop // display the results to the user cout << "\n\tHighest: " << highestScore; cout << "\n\tLowest: " << lowestScore; cout << endl; cin.get(); return 0; }// http://programmingnotes.org/ |
QUICK NOTES:
The highlighted lines are sections of interest to look out for.
The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.
Once compiled, you should get this as your output
Original array values
10 14 1 94 29 25 7 95 11 17 6 71 100 59
--------------------------------------------------------
These are the highest and lowest array values:
Highest: 100
Lowest: 1
Hi, I'm a software engineer. I write articles about programming and design in my spare time.
