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Day 5 Sample code

Using do-while to repeat program code

int main() {
    int x, y;
    char done;
    do {
        cout << "Input two numbers:";
        cin >> x >> y;
        cout << "Sum:" << x + y << endl;

        cout << "Do again? (Type y to repeat, anything else to stop):";
        cin >> done;
    } while (done == 'y');
    return 0;
}
 

Prime 1 - not quite right

#include<iostream>
 
using namespace std;
 
int main() {
    int num,count=0;
    cout<<"Enter the number to check : ";
    cin>>num;
    int i = 2;
    while (i<num){
        if(num%i==0) {       // checks if the number is fully divisible or not
            count++;
        }
        i++;
    }
    if(count==0) {
        cout<<"It is a Prime Number \n";
    } else {
 cout<<"It is not a Prime Number \n";
    }
}
 

Prime correct (for 1)

#include<iostream>
 
using namespace std;
 
int main() {
    int num,count=0;
    cout<<"Enter the number to check : ";
    cin>>num;
    
 int i = 2;
    while (i<num){
        if(num%i==0) {       // checks if the number is fully divisible or not
            count++;
        }
        i++;
    }
    if(num < 2 || count>0) {
     cout << num <<" is not a Prime Number \n";
    } else {
        cout << num <<" is a Prime Number \n";
 }
}
 

Prime faster

#include<iostream>
 using namespace std;
 
int main() {
    int num,count=0;
    cout<<"Enter the number to check : ";
    cin>>num;
    
    int i = 2;
    while (i<num && num%i!=0){
        i++;
    }
    if (i==num) {
        cout<<"It is a Prime Number \n";
    } else {
 cout<<"It is not a Prime Number \n";
 cout<<"The Number " << num << " is divisable by " << i << "\n";
 }
 
}

 

Prime with multiway

#include<iostream>
 using namespace std;
 
int main() {
    int num,count=0;
    cout<<"Enter the number to check : ";
    cin>>num;
    
    int i = 2;
    while (i<num && num%i!=0){
        i++;
    }
    if (num<2) {
     cout << num << " is not prive by definition";
    } else if (i==num) {
       cout << num <<" is a Prime Number \n";
    } else {
     cout<<"It is not a Prime Number \n";
     cout<<"The Number " << num << " is divisable by " << i << "\n";
  }
}

Prime with for statement

#include<iostream>
 
using namespace std;
 
int main() {
    int num,count=0;
    bool prime = true;
    cout<<"Enter the number to check : ";
    cin>>num;
 
    for(int i=2;i<num;i++){
        if(num%i==0) {       // checks if the number is fully divisible or not
            prime = false;
        }
    }
    if(prime) {
        cout<<"It is a Prime Number \n";
    } else {
 cout<<"It is not a Prime Number \n";
 }
}

Prime with break

#include<iostream>
 
using namespace std;
 
int main() {
    int num,count=0;
    bool prime = true;
    cout<<"Enter the number to check : ";
    cin>>num;
 
        if (num > 1) {
        for(int i=2;i<num;i++){
                if(num%i==0) {       // checks if the number is fully divisible or not
                prime = false;
                break;
                }
        }
        if(prime) {
                cout<<num << " is a Prime Number \n";
        } else {
                        cout<<num << " is not a Prime Number \n";
        }
    } else {
            cout << num << " is not prime by definition";
    }
 
}

Prime using square root

#include<iostream>
 
using namespace std;
#include <math.h>
 
int main() {
    int num,count=0;
    bool prime = true;
    cout<<"Enter the number to check : ";
    cin>>num;
    int max = sqrt(num);
 
  if (num > 1) {
     for(int i=2;i<=max;i++){
         if(num%i==0) {       // checks if the number is fully divisible or not
             prime = false;
             break;
         }
     }
     if(prime) {
         cout<<num << " is a Prime Number \n";
     } else {
                cout<<num << " is not a Prime Number \n";
     }
     } else {
  cout << num << " is not prime by definition";
     }
 
} 

Prime list

#include<iostream>
 
using namespace std;
#include <math.h>
 
int main() {
    int max,count=0;
    bool prime = true;
    cout<<"Enter the maximum number to check : ";
    cin>>max;
    
    for (int j=2 ; j<=max; j++) {
     prime = true;
     for(int i=2;i<= sqrt(j);i++){
         if(j%i==0) {      
             prime = false;
             break;
         }
     }
     if(prime) {
         cout << j << " ";
     } 
    }
    cout << "\nDone listing primes less than or equal to " << max << ".\n";
} 

Find Factors

#include <iostream>
#include <math.h>
using namespace std;

int main() {
 int n;
 bool prime = true;
 cout << "Enter a number to find it's factors:";
 cin >> n;
 cout << "Factors: ";
 for (int i = 2; i<= sqrt(n) ; i++) {
 if (n%i == 0) {
 cout << i << " ";
 prime = false;
 }
 }
 if (prime) {
 cout << "Prime, no factor other then 1 and " << n << endl;
 }
 return 0;
}

Switch Statement (grades)

DISPLAY 3.6 A switch Statement
//Program to illustrate the switch statement.
#include <iostream>
using namespace std;

int main( )
{
    char grade;

    cout << "Enter your midterm grade and press Return: ";
    cin >> grade;

    switch (grade)
    {
        case 'A':
            cout << "Excellent. "
                 << "You need not take the final.\n";
            break;
        case 'B':
            cout << "Very good. ";
            grade = 'A';
            cout << "Your midterm grade is now "
                 << grade << endl;
            break;
        case 'C':
            cout << "Passing.\n";
            break;
        case 'D':
        case 'F':
            cout << "Not good. "
                 << "Go study.\n";
            break;
        default:
            cout << "That is not a possible grade.\n";
    }

    cout << "End of program.\n";
    return 0;
}

A Menu

//DISPLAY 3.7 A Menu 
//Program to give out homework assignment information.
#include <iostream>
using namespace std;

 
int main( )
{
    int choice;

    do
    {
        cout << endl
             << "Choose 1 to see the next homework assignment.\n"
             << "Choose 2 for your grade on the last assignment.\n"
             << "Choose 3 for assignment hints.\n"
             << "Choose 4 to exit this program.\n"
             << "Enter your choice and press Return: ";
        cin >> choice;
 
        switch (choice)
        {
            case 1:
               //code to display the next assignment on screen would go here.
                break;
            case 2:
               //code to ask for a student number and give the corresponding 
               //grade would go here.
                break;
            case 3:
               //code to display a hint for the current assignment would go 
               //here.
                break;
            case 4:
                cout << "End of Program.\n";
                break;
            default:
                  cout << "Not a valid choice.\n"
                     << "Choose again.\n";
        }
    }while (choice != 4);

    return 0;
}

Local Variables

//DISPLAY 3.8 Block with a Local Variable
//Program to compute bill for either a wholesale or a retail purchase.
#include <iostream>
using namespace std;
const double TAX_RATE = 0.05; //5% sales tax.


int main( )
{
    char sale_type;
    int number;
    double price, total;

    cout << "Enter price $";
    cin >> price;
    cout << "Enter number purchased: ";
    cin >> number;
    cout << "Type W if this is a wholesale purchase.\n"
         << "Type R if this is a retail purchase.\n"
         << "Then press Return.\n";
    cin >> sale_type;

    if ((sale_type = = 'W') || (sale_type = = 'w'))
    {
        total = price * number;
    }
    else if ((sale_type = = 'R') || (sale_type = = 'r'))
    {
        double subtotal;
        subtotal = price * number;
        total = subtotal + subtotal * TAX_RATE;
    }
    else
    {
        cout << "Error in input.\n";
    }
    cout.setf(ios::fixed);
    cout.setf(ios::showpoint);
    cout.precision(2);
    cout << number << " items at $" << price << endl;
    cout << "Total Bill = $" << total;
    if ((sale_type = = 'R') || (sale_type = = 'r'))
        cout << " including sales tax.\n";

    return 0;
}

For Statement

//DISPLAY 3.12 A for Statement 
//Illustrates a for loop.
#include <iostream>
using namespace std;

int main( )
{
    int sum = 0;

    for (int n = 1; n <= 10; n++)  //Note that the variable n is a local
        sum = sum + n;             //variable of the body of the for loop!

    cout << "The sum of the numbers 1 to 10 is "
         << sum << endl;
    return 0;
}

break Statement

//DISPLAY 3.14 A break Statement in a Loop
//Sums a list of ten negative numbers.
#include <iostream>
using namespace std;

int main( )
{
    int number, sum = 0, count = 0;
    cout << "Enter 10 negative numbers:\n";

    while (++count <= 10) 
    {
        cin >> number;

        if (number >= 0)
        {
            cout << "ERROR: positive number"
                 << " or zero was entered as the\n"
                 << count << "th number! Input ends "
                 << "with the " << count << "th number.\n"
                 << count << "th number was not added in.\n";
            break;
        }

        sum = sum + number;
    }

    cout << sum << " is the sum of the first " 
         << (count - 1) << " numbers.\n";

    return 0;
}

Explicitly Nested Loops

//DISPLAY 3.15 Explicitly Nested Loops
//Determines the total number of green-necked vulture eggs
//counted by all conservationists in the conservation district.
#include <iostream>
using namespace std;

void instructions ();

int main()
{
cout << "This program tallies conservationist reports\n"
         << "on the green-necked vulture.\n"
         << "Each conservationist's report consists of\n"
         << "a list of numbers. Each number is the count of\n"
         << "the eggs observed in oneî 
         << "green-necked vulture nest.\n"
         << "This program then tallies 
         << "the total number of eggs.\n";

    int number_of_reports;
    cout << "How many conservationist reports are there? ";
    cin >> number_of_reports;

    int grand_total = 0, subtotal, count;
    for (count = 1; count <= number_of_reports; count++)
    {
        cout << endl << "Enter the report of "
             << "conservationist number " << count << endl;
        cout << "Enter the number of eggs in each nest.\n"
             << "Place a negative integer at the end of your list.\nî;î
        subtotal = 0;
       int next;
        cin >> next;
        while (next >=0)
        {
            subtotal = subtotal + next;
            cin >> next;
        }
        cout << "Total egg count for conservationist "
             << " number " << count << " is " 
             << subtotal << endl;
        grand_total = grand_total + subtotal;
    }
    cout << endl << "Total egg count for all reports = "
         << grand_total << endl;

    return 0;
}

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Topic revision: r7 - 2016-09-13 - JimSkon
 
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