How to loop certain aspects of a program - c++

I'm trying to loop the assignment scores and totals based on whatever the user inputs in for n. I have been searching around and just hitting duds, which is what the whole deal with the int i variable is at the moment. I can't get things to loop properly and right now this doesn't even compile because of that pesky i I have in there. You take out that i and the program runs fine with the exception that nothing becomes of the n input.
/**
File: project_2_14.cpp
Description: Write a program that calculates the total grade for N classroom exercises as a percentage. The user should input the value for N followed by each of the N scores and totals. Calculate the overall percentage (sum of the total points earned divided by the total points possible.) and output it as a percentage. Sample input and output is shown below.
Created: Friday, September 11th, 2015
Author:
email:
*/
#include<iostream>
#include<vector>
using namespace std;
int main()
{
float s; // assignment score
float t; // total points worth
float p; // percentage
int n = 0;
//input the number of assignments
cout << "How many assignments are there? " << endl;
cin >> n;
for (int i=0; i < =n; i++)
{
//input the total points earned for assignment
cout << "What is the score earned for this assignment? ";
cin >> s;
//input the number of points assignment is worth
cout << "How many points was the assignment worth? ";
cin >> t;
//calculate percentage
p = (s / t)*100;
}
//output score
cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(2);
cout << "Total score: " << p << "%"<< endl;
return 0;
}

You should remove the int n = 0; and it should be simply int n.
and you should use <=, without any spaces between both characters.
EDIT:
As you can see here: http://ideone.com/SeNum8 it already loops correctly :)
#include<iostream>
#include<vector>
using namespace std;
int main()
{
float s; // assignment score
float t; // total points worth
float p; // percentage
int n;
//input the number of assignments
cout << "How many assignments are there? " << endl;
cin >> n;
for (int i=0; i <=n; i++)
{
//input the total points earned for assignment
cout << "What is the score earned for this assignment? ";
cin >> s;
//input the number of points assignment is worth
cout << "How many points was the assignment worth? ";
cin >> t;
//calculate percentage
p = (s / t)*100;
}
//output score
cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(2);
cout << "Total score: " << p << "%"<< endl;
return 0;
}

Related

How to calculate inputted values using a while loop c++?

How do you use a while loop only to add multiple values with a given point when to exit the loop and display the tallied amounts.
Note the following example. Test your program by entering 7 for the number of items and the following values for the calories: 7 - 120 60 150 600 1200 300 200
If your logic is correct, the following will be displayed: Total calories eaten today = 2630
Below is what I have written, what I require is understanding the calculation for the total calories.
#include <iostream>
using namespace std;
int main()
{
int numberOfItems;
int count = 1; //loop counter for the loop
int caloriesForItem;
int totalCalories;
cout << "How many items did you eat today? ";
cin >> numberOfItems;
cout << "Enter the number of calories in each of the "
<< numberOfItems << " items eaten: " << endl;
while (count <= numberOfItems) // count cannot be more than the number of items
{
cout << "Enter calorie: ";
cin >> caloriesForItem;
totalCalories = ; //?
++count;
}
cout << "Total calories eaten today = " << totalCalories;
return 0;
}
How do I store a value, then add on that value, repeatedly until the program reaches a point to exit as per the count value
Logic Explained
Initialize totalCalories to 0 outside the loop. This is required to prevent undefined behaviour. You may refer to (Why) is using an uninitialized variable undefined behavior? and Default variable value.
For every item, add caloriesForItem to totalCalories. You may also use the += operator if you are familiar with it.
Sourcecode
#include <iostream>
using namespace std;
int main()
{
int numberOfItems;
int count = 1; //loop counter for the loop
int caloriesForItem;
long totalCalories = 0;
cout << "How many items did you eat today? ";
cin >> numberOfItems;
cout << "Enter the number of calories in each of the "
<< numberOfItems << " items eaten: " << endl;
while (count <= numberOfItems) // count cannot be more than the number of items
{
cout << "Enter calorie: ";
cin >> caloriesForItem;
totalCalories = totalCalories + caloriesForItem;
++count;
}
cout << "Total calories eaten today = " << totalCalories;
return 0;
}
Also you can add them with += operator. But the result will be the same.
totalCalories += caloriesForItem;
You should increase the number of total calories in every loop. You can easily do that using the addition assignment operator (+=). It should look like this :
totalCalories += caloriesForItem;

Stumped with a transient population program in c++

this is my first time posting on here. Whenever I've gotten stuck on a programming problem, I've typically been able to find enough information to get me unstuck. I'm afraid that the issue I'm having though, I can't quite find an answer to. It's something I'd need someone to look at to tell me what I may be doing wrong in my code.
I have the program running successfully, and it DOES work. The issue however, is that my produced output is off by a few numbers when compared to the expected output on My Programming Lab. I'm really not sure of what to do to produce the correct output. Allow me to post both my source code, and a screenshot MPL's results screen.
SOURCE CODE:
#include <iostream>
using namespace std;
int populationCalculator(int, double, double, int, int);
int main()
{
int startingPopulation, newArrivals, peopleWhoLeft, years,
newPopulation, finalPopulation;
double deathRate, birthRate;
cout << "This program calculates population change.\n";
cout << "Enter the starting population size: ";
cin >> startingPopulation;
while (startingPopulation < 2)
{
cout << "\nThe starting population may not be less than two. Please
re - enter: ";
cin >> startingPopulation;
}
cout << "Enter the annual birth rate (as % of current population): ";
cin >> birthRate;
while (birthRate < 0)
{
cout << "\nBirth rate percent cannot be negative. Please re -
enter:";
cin >> birthRate;
}
birthRate = birthRate / 100;
cout << "Enter the annual death rate (as % of current population): ";
cin >> deathRate;
while (deathRate < 0)
{
cout << "\nDeath rate percent cannot be negative. Please re -
enter: ";
cin >> deathRate;
}
deathRate = deathRate / 100;
cout << "How many individuals move into the area each year? ";
cin >> newArrivals;
while (newArrivals < 0)
{
cout << "\nArrivals cannot be negative. Please re - enter: ";
cin >> newArrivals;
}
cout << "How many individuals leave the area each year? ";
cin >> peopleWhoLeft;
while (peopleWhoLeft < 0)
{
cout << "\nDepartures cannot be negative. Please re - enter: ";
cin >> peopleWhoLeft;
}
cout << "For how many years do you wish to view population changes? ";
cin >> years;
while (years < 1)
{
cout << "\nYears must be one or more. Please re - enter: ";
cin >> years;
}
newPopulation = populationCalculator(startingPopulation, deathRate,
birthRate, newArrivals, peopleWhoLeft);
cout << "\nStarting population: " << startingPopulation << endl;
for (int loopCount = 1; loopCount <= years; loopCount++)
{
newPopulation = populationCalculator(newPopulation, deathRate,
birthRate, newArrivals, peopleWhoLeft);
cout << "Population at the end of year " << loopCount << " is: " <<
newPopulation << endl;
}
system("pause");
return 0;
}
int populationCalculator(int Population, double deathRate, double birthRate,
int newArrivals, int peopleWhoLeft)
{
int newPopulationCount;
newPopulationCount = Population + (Population * birthRate) - (Population
* deathRate) + newArrivals - peopleWhoLeft;
return newPopulationCount;
}
MPL RESULTS:
http://imgur.com/a/mRmpc
I really will appreciate if anyone can help me figure out why my produced output is off by a few numbers.
Step through your code. You're returning an int where you have double and int multiplication. Make sure that you aren't truncating values that might need to be rounded up or down.
Does birth happen before or after death? Should it occur in steps, or all at once like you have shown?
try casting to a double in your operations that involve doubles and integers. For example
birthRate = (double)(birthRate / 100);
deathRate = (double)(deathRate / 100);
Sometimes programming languages will cast a double to an integer, which causes your numbers to be off.
Perhaps the number were rounded off?
I assume this is the case because I noticed you declared some variables in double but the end result is integer. Try to change the data type of the method
populationCalculator(), newPopulation and of course the returning values of the method populationCalculator() from int to double.

C + + Can I use arrays here to shorten my code?

This is my first post on here so please don't kill me for my noobishness.
I recently made a program for fun to put in a ton of numbers and have it put out the mean, not very useful but I thought I would see if I could. I would love it if someone could explain to me how I could improve my code using arrays instead of lots of variables, but still achieve the same thing, maybe even more efficiently.
My code looks like this:
#include "stdafx.h"
#include <iostream>
using namespace std;
int main() {
int q1;
int q2;
int q3;
int q4;
int q5;
int q6;
int q7;
int q8;
int q9;
int q10;
int q11;
int q12;
int f;
//Used for the total of all values
int t;
//Used for the total to be divided
int a;
//Used for dividing the numbers.
cout << "We will be finding a mean. Enter the amount of numbers that will be entered, the maximum is 12: ";
cin >> a;
cout << "Now enter what numbers you want to find the mean for, because the maximum is 12, if you have less than 12, enter 0 for the rest: ";
cin >> q1;
cin >> q2;
cin >> q3;
cin >> q4;
cin >> q5;
cin >> q6;
cin >> q7;
cin >> q8;
cin >> q9;
cin >> q10;
cin >> q11;
cin >> q12;
f = q1 + q2 + q3 + q4 + q5 + q6 + q7 + q8 + q9 + q10 + q11 + q12;
cout << f / a << '\n';
system("pause");
}
Any advice is very appreciated! This was made in Visual Studio just in case you needed to know.
Of course arrays can make your life easier!
Here's how you could have accomplished the same task as above, with arrays:
#include "stdafx.h"
#include <iostream>
using namespace std;
int main() {
int totalNums;
cout << "We will be finding a mean.\n";
cout << "You can only enter up to 12 numbers;
// Declare an array to hold 12 int's
int nums[12];
// i will count how many numbers have been entered
// sum will hold the total of all numbers
int i, sum = 0;
for(i = 0; i < 12; i++) {
cout << "Enter the next number: ";
cin >> nums[i];
sum += nums[i];
}
cout << "The mean is: " << (sum / totalNums) << '\n';
//Try to avoid using system!
system("pause");
}
But, why use an array?
There's no need to keep any of the numbers after you add them to the total, so why use an array?
You can accomplish the same task without an array and with only one variable for the numbers!
#include "stdafx.h"
#include <iostream>
using namespace std;
int main() {
int totalNums;
cout << "We will be finding a mean.\n";
cout << "Enter the amount of numbers that will be entered: ";
cin >> totalNums;
// i will count how many numbers have been entered
// sum will hold the total of all numbers
// currentNum will hold the last number entered
int i, sum = 0, currentNum = 0;
for(i = 0; i < totalNums; i++) {
cout << "Enter the next number: ";
cin >> currentNum;
sum += currentNum;
}
cout << "The mean is: " << 1.0 * sum / totalNums << '\n';
//Try to avoid using system!
system("pause");
}
Arrays can be considered as series of variables each of which has ids.
integers between 0 and (number of elements) - 1 (both inclusive) are available ids.
Using that with loop, your code can be like this (sorry, I hate stdafx.h):
#include <cstdlib>
#include <iostream>
using namespace std;
int main() {
int q[12];
int f;
//Used for the total of all values
int t;
//Used for the total to be divided
int a;
//Used for dividing the numbers.
cout << "We will be finding a mean. Enter the amount of numbers that will be entered, the maximum is 12: ";
cin >> a;
cout << "Now enter what numbers you want to find the mean for, because the maximum is 12, if you have less than 12, enter 0 for the rest: ";
for (int i = 0; i < 12; i++) {
cin >> q[i];
}
f = 0;
for (int i = 0; i < 12; i++) {
f += q[i];
}
cout << f / a << '\n';
system("pause");
}
You may use the numbers read in the future, but currently the numbers aren't used except for calculating the sum, so you can omit the array and do addition while reading. Also I deleted the variable t, which is unused and stopped using using namespace std;, which is not considered as good.
#include <cstdlib>
#include <iostream>
using std::cin;
using std::cout;
int main() {
int q;
int f;
//Used for the total of all values
int a;
//Used for dividing the numbers.
cout << "We will be finding a mean. Enter the amount of numbers that will be entered, the maximum is 12: ";
cin >> a;
cout << "Now enter what numbers you want to find the mean for, because the maximum is 12, if you have less than 12, enter 0 for the rest: ";
f = 0;
for (int i = 0; i < 12; i++) {
cin >> q;
f += q;
}
cout << f / a << '\n';
system("pause");
}
You marked this question as C++.
I recommend you do not use "using", and you should prefer vector over array.
Consider the following approach:
#include <iostream>
#include <vector>
int main(int argc, char* argv[])
{
std::cout << "We will be finding a mean." << std::endl
<< "Enter numbers, and press ^d when complete.\n"
<< std::endl;
// Declare a vector to hold user entered int's
std::vector<int> intVec;
// the vector automatically keeps track of element count
do {
std::cout << "number: "; // prompt
int t = 0;
std::cin >> t; // use std::cin,
if(std::cin.eof()) break; // ^d generates eof()
intVec.push_back(t);
}while(1);
// there are several way to sum a vec,
// this works fine:
int sum = 0;
for (auto i : intVec) sum += i;
std::cout << "\n sum : " << sum
<< "\ncount : " << intVec.size()
<< "\n mean : " << (sum / intVec.size()) << std::endl;
return(0);
}
You can enter single item per line (neatness counts).
You can enter multiple integers separated by white space, but the above will give back a prompt for the integers already entered.
^d - generates an end of file input.
... press and hold 'Control' key and letter 'd' at same time
Note - does not handle error input - try entering a 'number' as 'num' string.
The accepted answer is definitely the most efficient way to transform your code using arrays, but one thing I would add is that in C++ dividing an integer by another integer can only ever result in an integer, and because you're trying to get the mean, it seems like you'd want to have the result in decimals, so you need to do one of two things:
Declare sum as a float for the purposes of diving it by totalNums to get the mean.
Cast one of the integers to either a float or a double so that the decimals won't get truncated, so the last cout statement would look like this:
cout << "The mean is: " << (double)sum/totalNums << endl;
In C++ the default for precision is 6, but you can change the number of decimal points that are displayed by adding #include <iomanip> and using the setprecision( ) function in the iomanip, which you can just add in the same output line:
cout << setprecision(x) << "The mean is: " << (double)sum/totalNums << endl;
where x is whatever precision you want.
If you want to try using dynamic memory
This is definitely not necessary for what you're doing, but it's interesting stuff and good practice!
One more thing is that if you want to be able to have the user enter integers indefinitely, you can dymanically allocate memory during runtime by declaring a array of pointers to integers (so it's an array of address locations instead of an array of integers) and some sentinal value so they can decide when to stop. That code would look like:
#include <iostream>
#include <iomanip>
using namespace std;
main( ) {
const int ARRAY_SIZE = 200;
const int SENTINAL = -999;
int totalNums = 0;
int sum = 0;
//declare an array of pointers to integers so
//the user can enter a large number of integers
//without using as much memory, because the memory
//allocated is an array of pointers, and the int
//aren't allocated until they are needed
int *arr[ARRAY_SIZE];
cout << "We will be finding a mean." << endl;
cout << "Enter integers (up to 200) or enter -999 to stop" << endl;
//add a conditional into the for loop so that if the
//user enters the sentinal value they will break out
//of the loop
for (int c = 0; c < ARRAY_SIZE; c++) {
//every time you iterate through the loop, create a new
//integer by using the new keyword using totalNums as
//the index
arr[totalNums] = new int;
cout << "Enter integer: ";
//input into the array of pointers by dereferencing it
//(so it refers to what the pointer is pointer to instead
//of the pointer)
cin >> *arr[totalNums];
if (*arr[totalNums] == SENTINAL)
break;
else {
sum += *arr[totalNums];
totalNums++;
}
}
cout << setprecision(3) << "The mean is: " << (float)sum / totalNums << endl;
}

C++ Airfare Charge Calculation project

I have to create a program to calculate charges for airfare. It's a simple program so far and I am not done adding to it, but every time I run it the result turns out to be 0. Is there something missing in my code? I am a beginner and I would appreciate any advice on improving my code. Thank you.
#include <iostream>
using namespace std;
void main () {
int distance = 0;
int num_bags= 0;
int num_meals= 0;
double distance_price = distance * 0.15;
double bag_price = num_bags * 25.00;
double meal_price = num_meals * 10.00;
double total_airfare = 0.00;
cout << "CorsairAir Fare Calculator" << endl;
cout << "Enter the distance being travelled: " << endl;
cin >> distance;
cout << "Enter number of bags checked: " <<endl;
cin >> num_bags;
cout << "Enter the number of meals ordered: " << endl;
cin >> num_meals;
total_airfare = (distance_price + bag_price + meal_price);
cout << total_airfare;
}
Your confusion is completely understandable - the piece you're missing is that when you assign a variable, you're assigning the left side to the result of the right side at that moment in time. It's not like algebra, where you say f(x) = x + 5 and f(x) is always whatever x + 5 is.
So, you assign double distance_price = distance * 0.15 when distance is 0 (which you just initialized). distance_price remains 0 even after you ask for input and change distance.
Do your price calculations after you ask for input, and everything will work just fine.
You are calculating the distance_price bag_price meal_price with default values i.e. 0 not with the value which you took from user.
Below code works fine and you won't see the issue.
#include <iostream>
using namespace std;
// My compiler did not allow void main so used int main
int main () {
int distance = 0;
int num_bags= 0;
int num_meals= 0;
double distance_price ;
double bag_price ;
double meal_price;
double total_airfare;
cout << "CorsairAir Fare Calculator" << endl;
cout << "Enter the distance being travelled: " << endl;
cin >> distance;
cout << "Enter number of bags checked: " <<endl;
cin >> num_bags;
cout << "Enter the number of meals ordered: " << endl;
cin >> num_meals;
distance_price = distance * 0.15;
bag_price = num_bags * 25.00;
meal_price = num_meals * 10.00;
total_airfare = 0.00;
total_airfare = distance_price + bag_price + meal_price;
cout << total_airfare;
return 0;
}
Result
CorsairAir Fare Calculator
Enter the distance being travelled:
200
Enter number of bags checked:
2
Enter the number of meals ordered:
2
100

Trouble with dynamic arrays and finding the sum of values

So as I explained in the title i'm having trouble trying to get the sum of an array. I've just now learned how to create dynamic arrays and I did some searching on how to calculate the sum. I don't believe I fully understand what is going on to calculate the sum.
// Final Grade Calculator
#include <cstdlib>
#include <iostream>
#include <cmath>
#include <string>
using namespace std;
int main(){
double minor, quiz, major;
int minorG, quizG, majorG;
minorG = 0;
cout << "Final Grade Calculator" << endl;
cout << "Input minor grade weight percent." << endl;
cin >>minor;
cout << "Input quiz grade weight percent." << endl;
cin >>quiz;
cout << "Input major grade weight percent." << endl;
cin >>major;
// Three grade categories
minor = minor/100;
quiz = quiz/100;
major = major/100;
for(int i = 1; i <=10; i++){
cout << "Input a minor grade. (Max=10)" << endl;
cin >>minorG;
int *minorGA = new int[minorG];
minorG+= minorGA[minorG];
cout << "Currently: " << i << " Grade(s)." <<endl;
}
cout << "Minor Sum: " << minorG << endl;
return 0;
}
This is what I have so far and the trouble I am having is within the for loop which is where my array is and where I am trying to get the sum of it. When I compile and run I get a sum of 138,427. Any help would be greatly appreciated!
I think you're over-complicating things with dynamic arrays. I'll explain what you're doing, and try to provide help for what I think you're trying to do.
In your code int* minorGA = new int[minorG]; you are allocating memory for minorG amount of ints. There are two problems here:
You are accessing an element outside of the memory you allocated. When you allocate 10 elements, you can access elements 0-9. Trying to access 10 is undefined behaviour (you are trying to access parts of memory that could contain anything).
The values stored in this array are just whatever is in memory, so when you are attempting to increment minorG by the amount of one of these, it's just whatever is in memory at the time.
A separate problem is that you are not deallocating the memory, but some might argue that it isn't really a problem.
You should just be able to have the following to perform what I think you're trying to do:
for (int i = 0; i < 10; ++i)
{
int inputtedNumber = 0;
cout << "Enter a number" << endl;
cin >> inputtedNumber;
// add that number to some tally:
finalTally += inputtedNumber;
}
Or if you are trying to store the elements in an array, you can use the following:
const int maxElements = 10;
int grades[maxElements] = {}; // this will construct all elements with 0. Without this, the elements may contain any number.
for (int i = 0; i < maxElements; ++i)
{
int inputtedNumber = 0;
cout << "Enter a number" << endl;
cin >> inputtedNumber;
// Store the number
grades[i] = inputtedNumber;
}
In saying that, it will be better to use std::vector (knows its size, handles memory for you, can grow):
std::vector<int> grades;
// Allow the user to enter as many numbers as they'd like
for (;;)
{
int input = 0;
cout << "Enter a number" endl;
cin >> input;
// Store the number. Will continue to grow
grades.push_back(input);
}