(Sorry if this is formatted terribly. I've never posted before.)
I've been working on a program for class for a few hours and I can't figure out what I need to do to my function to get it to do what I want. The end result should be that addUnique will add unique inputs to a list of its own.
#include <iostream>
using namespace std;
void addUnique(int a[], int u[], int count, int &uCount);
void printInitial(int a[], int count);
void printUnique(int u[], int uCount);
int main() {
//initial input
int a[25];
//unique input
int u[25];
//initial count
int count = 0;
//unique count
int uCount = 0;
//user input
int input;
cout << "Number Reader" << endl;
cout << "Reads back the numbers you enter and tells you the unique entries" << endl;
cout << "Enter 25 positive numbers. Enter '-1' to stop." << endl;
cout << "-------------" << endl;
do {
cout << "Please enter a positive number: ";
cin >> input;
if (input != -1) {
a[count++] = input;
addUnique(a, u, count, uCount);
}
} while (input != -1 && count < 25);
printInitial(a, count);
printUnique(u, uCount);
cout << "You entered " << count << " numbers, " << uCount << " unique." << endl;
cout << "Have a nice day!" << endl;
}
void addUnique(int a[], int u[], int count, int &uCount) {
int index = 0;
for (int i = 0; i < count; i++) {
while (index < count) {
if (u[uCount] != a[i]) {
u[uCount++] = a[i];
}
index++;
}
}
}
void printInitial(int a[], int count) {
int lastNumber = a[count - 1];
cout << "The numbers you entered are: ";
for (int i = 0; i < count - 1; i++) {
cout << a[i] << ", ";
}
cout << lastNumber << "." << endl;
}
void printUnique(int u[], int uCount) {
int lastNumber = u[uCount - 1];
cout << "The unique numbers are: ";
for (int i = 0; i < uCount - 1; i++) {
cout << u[i] << ", ";
}
cout << lastNumber << "." << endl;
}
The problem is my addUnique function. I've written it before as a for loop that looks like this:
for (int i = 0; i < count; i++){
if (u[i] != a[i]{
u[i] = a[i]
uCount++;
}
}
I get why this doesn't work: u is an empty array so comparing a and u at the same spot will always result in the addition of the value at i to u. What I need, is for this function to scan all of a before deciding whether or no it is a unique value that should be added to u.
If someone could point me in the right direction, it would be much appreciated.
Your check for uniqueness is wrong... As is your defintion of addUnique.
void addUnique(int value, int u[], int &uCount)
{
for (int i = 0; i < uCount; i++){
if (u[i] == value)
return; // already there, nothing to do.
}
u[uCount++] = value;
}
Related
I finished this code homework assignment tonight. I thought I was done, but I just realized that my "Average" value is coming out wrong with certain values. For example: When my professor entered the values 22, 66, 45.1, and 88 he got an "Average" of 55.27. However, when I enter those values in my program, I get an "Average" of 55.25. I have no idea what I am doing wrong. I was pretty confident in my program until I noticed that flaw. My program is due at midnight, so I am clueless on how to fix it. Any tips will be greatly appreciated!
Code Prompt: "Write a program that dynamically allocates an array large enough to hold a user-defined number of test scores. Once all the scores are entered, the array should be passed to a function that sorts them in ascending order. Another function should be called that calculates the average score. The program should display the sorted list of scores and averages with appropriate headings. Use pointer notation rather than array notation whenever possible."
Professor Notes: The book only states, "Input Validation: Do not accept negative numbers for test scores." We also need to have input validation for the number of scores. If it is negative, including 0, the program halts, we should consider this situation for 'counter' not to be negative while we have a loop to enter numbers. So negative numbers should be rejected for the number of scores and the values of scores.
Here is my code:
#include <iostream>
#include <iomanip>
using namespace std;
void showArray(double* array, int size);
double averageArray(double* array, int size);
void orderArray(double* array, int size);
int main()
{
double* scores = nullptr;
int counter;
double numberOfScores;
cout << "\nHow many test scores will you enter? ";
cin >> numberOfScores;
if (numberOfScores < 0) {
cout << "The number cannot be negative.\n"
<< "Enter another number: ";
cin >> numberOfScores;
}
if (numberOfScores == 0) {
cout << "You must enter a number greater than zero.\n"
<< "Enter another number: ";
cin >> numberOfScores;
}
scores = new double[numberOfScores];
for (counter = 0; counter < numberOfScores; counter++) {
cout << "Enter test score " << (counter + 1) << ": ";
cin >> *(scores + counter);
if (*(scores + counter) < 0) {
cout << "Negative scores are not allowed. " << endl
<< "Enter another score for this test : ";
cin >> *(scores + counter);
}
}
orderArray(scores, counter);
cout << "\nThe test scores in ascending order, and their average, are: " << endl
<< endl;
cout << " Score" << endl;
cout << " -----" << endl
<< endl;
showArray(scores, counter);
cout << "\nAverage Score: "
<< " " << averageArray(scores, counter) << endl
<< endl;
cout << "Press any key to continue...";
delete[] scores;
scores = nullptr;
system("pause>0");
}
void orderArray(double* array, int size)
{
int counterx;
int minIndex;
int minValue;
for (counterx = 0; counterx < (size - 1); counterx++) {
minIndex = counterx;
minValue = *(array + counterx);
for (int index = counterx + 1; index < size; index++) {
if (*(array + index) < minValue) {
minValue = *(array + index);
minIndex = index;
}
}
*(array + minIndex) = *(array + counterx);
*(array + counterx) = minValue;
}
}
double averageArray(double* array, int size)
{
int x;
double total{};
for (x = 0; x < size; x++) {
total += *(array + x);
}
double average = total / size;
return average;
}
void showArray(double* array, int size)
{
for (int i = 0; i < size; i++) {
cout << " " << *(array + i) << endl;
}
}
I try to start my answers with a brief code review:
#include <iostream>
#include <iomanip>
using namespace std; // Bad practice; avoid
void showArray(double* array, int size);
double averageArray(double* array, int size);
void orderArray(double* array, int size);
int main()
{
double* scores = nullptr;
int counter;
double numberOfScores;
cout << "\nHow many test scores will you enter? ";
cin >> numberOfScores;
// This is not input validation, I can enter two consecutive bad values,
// and the second one will be accepted.
if (numberOfScores < 0) {
// Weird formatting, this blank line
cout << "The number cannot be negative.\n"
<< "Enter another number: ";
cin >> numberOfScores;
}
// The homework, as presented, doesn't say you have to treat 0 differently.
if (numberOfScores == 0) {
cout << "You must enter a number greater than zero.\n"
<< "Enter another number: ";
cin >> numberOfScores;
}
scores = new double[numberOfScores];
// Declare your loop counter in the loop
for (counter = 0; counter < numberOfScores; counter++) {
cout << "Enter test score " << (counter + 1) << ": ";
cin >> *(scores + counter);
if (*(scores + counter) < 0) {
cout << "Negative scores are not allowed. " << endl
<< "Enter another score for this test : ";
cin >> *(scores + counter);
}
}
orderArray(scores, counter); // Why not use numberOfScores?
cout << "\nThe test scores in ascending order, and their average, are: " << endl
<< endl;
cout << " Score" << endl;
cout << " -----" << endl
<< endl;
showArray(scores, counter); // Same as above.
cout << "\nAverage Score: "
<< " " << averageArray(scores, counter) << endl
<< endl;
cout << "Press any key to continue...";
delete[] scores;
scores = nullptr;
system("pause>0"); // Meh, I suppose if you're on VS
}
void orderArray(double* array, int size)
{
int counterx;
int minIndex;
int minValue; // Unnecessary, and also the culprit
// This looks like selection sort
for (counterx = 0; counterx < (size - 1); counterx++) {
minIndex = counterx;
minValue = *(array + counterx);
for (int index = counterx + 1; index < size; index++) {
if (*(array + index) < minValue) {
minValue = *(array + index);
minIndex = index;
}
}
*(array + minIndex) = *(array + counterx);
*(array + counterx) = minValue;
}
}
double averageArray(double* array, int size)
{
int x;
double total{};
for (x = 0; x < size; x++) {
total += *(array + x);
}
double average = total / size;
return average;
}
void showArray(double* array, int size)
{
for (int i = 0; i < size; i++) {
cout << " " << *(array + i) << endl;
}
}
When you are sorting your array, you keep track of the minValue as an int and not a double. That's why your average of the sample input is incorrect. 45.1 is truncated to 45 for your calculations. You don't need to keep track of the minValue at all. Knowing where the minimum is, and where it needs to go is sufficient.
But as I pointed out, there are some other serious problems with your code, namely, your [lack of] input validation. Currently, if I enter two consecutive bad numbers, the second one will be accepted no matter what. You need a loop that will not exit until a good value is entered. It appears that you are allowed to assume that it's always a number at least, and not frisbee or any other non-numeric value.
Below is an example of what your program could look like if your professor decides to teach you C++. It requires that you compile to the C++17 standard. I don't know what compiler you're using, but it appears to be Visual Studio Community. I'm not very familiar with that IDE, but I imagine it's easy enough to set in the project settings.
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <string>
#include <vector>
// Assumes a number is always entered
double positive_value_prompt(const std::string& prompt) {
double num;
std::cout << prompt;
do {
std::cin >> num;
if (num <= 0) {
std::cerr << "Value must be positive.\n";
}
} while (num <= 0);
return num;
}
int main() {
// Declare variables when you need them.
double numberOfScores =
positive_value_prompt("How many test scores will you enter? ");
std::vector<double> scores;
for (int counter = 0; counter < numberOfScores; counter++) {
scores.push_back(positive_value_prompt("Enter test score: "));
}
std::sort(scores.begin(), scores.end());
for (const auto& i : scores) {
std::cout << i << ' ';
}
std::cout << '\n';
std::cout << "\nAverage Score: "
<< std::reduce(
scores.begin(), scores.end(), 0.0,
[size = scores.size()](auto mean, const auto& val) mutable {
return mean += val / size;
})
<< '\n';
}
And here's an example of selection sort where you don't have to worry about the minimum value. It requires that you compile to C++20. You can see the code running here.
#include <iostream>
#include <random>
#include <vector>
void selection_sort(std::vector<int>& vec) {
for (int i = 0; i < std::ssize(vec); ++i) {
int minIdx = i;
for (int j = i + 1; j < std::ssize(vec); ++j) {
if (vec[j] < vec[minIdx]) {
minIdx = j;
}
}
int tmp = vec[i];
vec[i] = vec[minIdx];
vec[minIdx] = tmp;
}
}
void print(const std::vector<int>& v) {
for (const auto& i : v) {
std::cout << i << ' ';
}
std::cout << '\n';
}
int main() {
std::mt19937 prng(std::random_device{}());
std::uniform_int_distribution<int> dist(1, 1000);
std::vector<int> v;
for (int i = 0; i < 10; ++i) {
v.push_back(dist(prng));
}
print(v);
selection_sort(v);
print(v);
}
I opted not to give your code the 'light touch' treatment because than I would have done your homework for you, and that's just not something I do. However, the logic shown should still be able to guide you toward a working solution.
For an assignment, we were to fill an array with user-defined characters that stops filling once the user enters a full stop ".". Part of the assignment is to print out the characters entered in the array in reverse, but what I have seems to just print nothing.
First time asking, so apologies if it's a silly question. Thanks in advance.
#include <iostream>
using namespace std;
//Function declarations
bool fillArray(char charArray[], int arraySize, int& numberUsed);
void outputInReverse(const char charArray[], int& numberUsed);
int main() {
const int arraySize = 100;
char charArray[arraySize] = { };
int numberUsed = 0;
//Function calls
cout << "\nFILLING ARRAY....\n";
fillArray(charArray, arraySize, numberUsed);
cout << "\nARRAY OUTPUT....\n";
outputInReverse(charArray, numberUsed);
}
//Function definitions
bool fillArray(char charArray[], int arraySize, int& numberUsed) {
char inputChar;
int index = 0;
const char sentinel = '.';
bool sentinelEntered = false;
bool arrayFull = false;
int count = 0;
//Take user input
for (int i = 0; i < arraySize; i++) {
if ((!sentinelEntered)) {
cout << "Enter up to " << arraySize << " character values. Enter full stop to end. " << "Enter char " << (i + 1) << ": " << endl;
cin >> inputChar;
charArray[index] = inputChar;
//How many entries made
numberUsed = i;
count++;
if ((inputChar == sentinel)) {
sentinelEntered = true;
cout << "Number of entries: " << (count - 1) << endl;
return count;
}
}
}
if (numberUsed == arraySize) {
arrayFull = true;
return arrayFull;
}
return sentinelEntered;
return count;
}
// Reverse
void outputInReverse(const char charArray[], int& numberUsed) {
for (int i = numberUsed; i > 0; i--) {
cout << "Output in reverse: " << charArray[i] << endl;
}
}
FILLING ARRAY....
Enter up to 100 character values. Enter full stop to end. Enter char 1:
a
Enter up to 100 character values. Enter full stop to end. Enter char 2:
b
Enter up to 100 character values. Enter full stop to end. Enter char 3:
c
Enter up to 100 character values. Enter full stop to end. Enter char 4:
d
Enter up to 100 character values. Enter full stop to end. Enter char 5:
e
Enter up to 100 character values. Enter full stop to end. Enter char 6:
.
Number of entries: 5
ARRAY OUTPUT....
Output in reverse:
Output in reverse:
Output in reverse:
Output in reverse:
Output in reverse:
Not sure what you are trying to return from fillArray(), but since its a bool type, assuming you are trying to return if the array is empty or not. Observe added comments to see corrections.
int main() {
const int arraySize = 100;
//corrected
char charArray[arraySize] = { NULL };
int numberUsed = 0;
//Function calls
cout << "\nFILLING ARRAY....\n";
fillArray(charArray, arraySize, numberUsed);
cout << "\nARRAY OUTPUT....\n";
outputInReverse(charArray, numberUsed);
return 0;
}
bool fillArray(char charArray[], int arraySize, int& numberUsed) {
char inputChar;
int index = 0;
const char sentinel = '.';
bool sentinelEntered = false;
bool arrayFull = false;
int count = 0;
//Take user input
for (int i = 0; i < arraySize; i++) {
if ((!sentinelEntered)) {
cout << "Enter up to " << arraySize << " character values. Enter full stop to
end. " << "Enter char " << (i + 1) << ": " << endl;
cin >> inputChar;
//corrected: shifted here so before '.' can enter into array we return
if ((inputChar == sentinel)) {
sentinelEntered = true;
cout << "Number of entries: " << (count) << endl;
//correction: update numberUsed before returning and no of
//elements = count
numberUsed = i;
return count;
}
//correction: array index should not be "index" but i
charArray[i] = inputChar;
//How many entries made
numberUsed = i;
count++;
}
}
if (numberUsed == arraySize)
return true;
return false;
}
void outputInReverse(const char charArray[], int& numberUsed) {
for (int i = numberUsed-1; i >= 0; i--) {
cout << "Output in reverse: " << charArray[i] << endl;
}
}
#include <iostream>
#include <iomanip>
using namespace std;
// Function Prototype
void sortArray(int array[], int size);
void showArray(const int arr[], int size);
void average(int testScores[], int size);
int main()
{
int *testScores;
int numGrades,count;
cout << "How many grades? " << endl;
cin >> numGrades;
testScores = new int[numGrades];
cout << "Please enter the scores below." << endl;
for (count = 0; count < numGrades; count++)
{
cin >> testScores[count];
}
sortArray(testScores, numGrades);
showArray(testScores, numGrades);
average(testScores, numGrades);
delete[] testScores;
testScores = 0;
system("pause");
return (0);
}
//function for ascending order
int * testScores[];
void sortArray(int array[], int size)
{
bool swap;
int temp;
do
{
swap = false;
for (int count = 0; count < (size - 1); count++)
{
if (array[count]> array[count + 1])
{
temp = array[count];
array[count] = array[count + 1];
array[count + 1] = temp;
swap = true;
}
}
} while (swap);
}
// display array function
void showArray(const int arr[], int size)
{
cout << " Scores in ascending order." << endl;
for (int count = 0; count < size; count++)
{
cout << " " << arr[count] << "";
}
cout << endl;
cout << endl;
}
// function to get average of the array
void average(int testScores[], int numGrades)
{
float total = 0.0;
for (int count = 0; count < numGrades; count++)
{
total += testScores[count];
}
float average = total / numGrades;
cout << " This is the average of the scores entered." << endl;
cout << endl;
cout << fixed << showpoint << setprecision(2);
cout << " *** " << average << " ***" << endl;
}
So this program was made to allow students to enter as many test scores as they want and the program will show them in ascending order and then will calculate the average of all test scores. It works wonderful until you enter a negative test score and then it throws the averaging process off. I can't seem to be able to make the program not accept the negative numbers. Any clues or hints would work wonders! Please and Thank You.
You are doing this:-
cin >> testScores[count];
This would accept all integers positive as well as negative. One way is to check the number, if it's positive then insert it into array.
i am relatively new to programming, i just learned c++ and i am getting 2 errors for a HW assignment from school;
Error 2 error C4700: uninitialized local variable 'searchValueptr' used Line 83
and
Error 3 error C4703: potentially uninitialized local pointer variable 'createdArray' used
Line 70
I cannot for the life of me figure out why or how to fix it can some one help me please.
#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib>
#include <ctime>
using namespace std;
// prototypes
int *createArray(int &size);
void findStats(int *arr, int size, int &min, int &max, double &average);
int *searchElement(int *arr, int size, int *element);
int main ()
{
int choice, size;
bool menuOn = true;
while (menuOn == true)
{
cout << "1 - Create and initialize a dynamic array.\n";
cout << "2 - Display statistics on the array.\n";
cout << "3 - Search for an element.\n";
cout << "4 - Exit.\n";
cout << "Enter your choice and press return: ";
cin >> choice;
cout << endl;
switch (choice)
{
case 1:
int *createdArray;
cout << "Please enter a size for the array: ";
cin >> size;
createdArray = createArray(size);
for (int x=0; x < size; x++)
{
cout << "Value of array at index " << x << ": " << createdArray[x] << endl;
}
cout << endl;
break;
case 2:
int minNum;
int maxNum;
double avgNum;
findStats(createdArray, size, minNum, maxNum, avgNum);
cout << endl << "The maximum number is: " << maxNum;
cout << endl << "The minimum number is: " << minNum;
cout << endl << "The average number is: " << avgNum;
cout << endl << endl;
break;
case 3:
int *searchValueptr;
int searchValue;
cout << "Enter a value to search for: ";
cin >> searchValue;
*searchValueptr = searchValue;
searchElement(createdArray, size, searchValueptr);
break;
case 4:
cout << "Thanks for using this program";
menuOn = false;
break;
default:
cout << "Not a Valid Choice. \n";
cout << "Choose again.\n";
cin >> choice;
break;
}
}
cout << endl;
system("pause");
return 0;
} // end function main ()
int *createArray(int &size)
{
unsigned seed = time(0);
srand(seed);
int *randArray = new int [size];
for (int x=0; x < size; x++)
{
randArray[x] = rand();
}
cout << endl;
return randArray;
}
void findStats(int *arr, int size, int &min, int &max, double &average)
{
min = arr[0];
max = arr[0];
double sum = 0;
for (int count = 0; count < size; count++)
{
if (min >= arr[count])
{
min = arr[count];
}
if (max <= arr[count])
{
max = arr[count];
}
sum += arr[count];
}
average = sum/size;
}
int *searchElement(int *arr, int size, int *element)
{
bool match = false;
for (int count = 0; count < size; count++)
{
if (arr[count] == *element)
{
match = true;
}
}
if (match)
{
cout << "Match Found at: " << element;
return element;
}
else
{
cout << "No Found";
return 0;
}
}
either use
searchValueptr = &searchValue;
or send the pass the address of searchValue
searchElement(createdArray, size, &searchValue);
break;
My code is done and working. But i cant figure out how to count the number of attempts made by the user and invalid account numbers that were entered. I am supposed to do this in main starting after cin >> accountNum. After the user enters 9999 to quit, it is supposed to display the number of attempts made and the number of invalid charge account numbers that were entered. When i run it i get 0 for number of attempts and -1 for invalid numbers entered.
#include <iomanip>
#include <iostream>
#include <fstream>
using namespace std;
void getAccountNumbers(int[], int);
void displayAccountNumbers(int[], int);
void selectionSort(int[], int);
int binarySearch(const int[], int, int);
int main()
{
int accountNum;
int results;
int attempts = 0;
int invalidNumbers = 0;
const int ARRAY_SIZE = 18; // Array size
int numbers[ARRAY_SIZE]; // Array with 18 elements
int count = 0;
//ifstream inputFile;
getAccountNumbers(numbers, ARRAY_SIZE);
cout << "Original Order" << endl;
displayAccountNumbers(numbers, ARRAY_SIZE);
selectionSort(numbers, ARRAY_SIZE);
cout << "Sorted List" << endl;
displayAccountNumbers(numbers, ARRAY_SIZE);
cout << "********************" << endl;
cout << "Enter an Account number or 9999 to quit" << endl;
cin >> accountNum;
if(accountNum == 9999)
{
cout << "Thank You!" << endl;
}
while(accountNum != 9999)
{
results = binarySearch(numbers, ARRAY_SIZE, accountNum);
if(results == -1)
{
cout << "That number was not found" << endl;
invalidNumbers = results++;
}
else
{
cout << "That number is valid " << endl;
}
attempts = results++;
cin >> accountNum;
}
cout << "Number of attempts: " << attempts << endl;
cout << "Invalid numbers entered: " << invalidNumbers << endl;
system("pause");
return 0;
}
void getAccountNumbers(int nums[], int size)
{
ifstream inputFile;
int count = 0;
//Open the file
inputFile.open("charges.txt");
while(count < size && inputFile >> nums[count])
count ++;
//Close the file
inputFile.close();
}
void displayAccountNumbers(int nums[], int size)
{
for(int count = 0; count < size; count++)
cout << nums[count] << "\t";
cout << endl << endl;
}
void selectionSort(int nums[], int size)
{
int startScan, minIndex, minValue;
for(startScan = 0; startScan < (size - 1); startScan++)
{
minIndex = startScan;
minValue = nums[startScan];
for(int index = startScan + 1; index < size; index++)
{
if(nums[index] < minValue)
{
minValue = nums[index];
minIndex = index;
}
}
nums[minIndex] = nums[startScan];
nums[startScan] = minValue;
}
}
int binarySearch(const int nums[], int size, int value)
{
int first = 0, //First element
last = size - 1, // Last element
middle, // Midpoint
position = -1; //Position of search value
bool found = false;
while(!found && first <= last)
{
middle = (first + last) / 2; //Midpoint
if(nums[middle] == value)
{
found = true;
position = middle;
}
else if(nums[middle] > value) // Value is in lower half
last = middle - 1;
else
first = middle + 1; // Value is in upper half
}
return position;
}
Your problem is in the lines where you are trying to add to invalidNumbers and attempts. The ++ postfix operator adds one to the number before it. You needn't say invalidNumbers = results++;; you merely need invalidNumbers++;, and the same applies for attempts. What your code was doing was setting invalidNumbers (and attempts) to the value of results and then adding one to results instead.