I'm trying to create a program where you input 20 characters into an array. Each time you enter a new character, the program should check if that character is already in the array, if it is, print duplicate (but still add the duplicate to the array)
For example, if user types 'a', program should check if 'a' is inside the array.
This is my code:
#include <iostream>
using namespace std;
int main() {
char myAlpha[20];
char input;
cout << "Enter a letter" << endl;
for (int i= 0; i <= 20; i++) {
cin >> input;
for (int k = 0; k <= 20; k++) {
if (myAlpha[k] == input)
cout << "Duplicate" << endl;
}
myAlpha[i] = input;
}
}
I just can't figure out how to make it work, I'm probably missing something stupid. The solution must use something like the code above, no fancy functions or anything.
EDIT: Fixed Code:
#include <iostream>
using namespace std;
int main() {
char myAlpha[20];
char input;
cout << "Enter a letter" << endl;
for (int i= 0; i < 20; i++) {
cin >> input;
for (int k = 0; k < i; k++) {
if (myAlpha[k] == input)
cout << "Duplicate" << endl;
}
myAlpha[i] = input;
}
}
Only problem is that "duplicate" is printed a extra time for each duplication of a letter. For example, if 'a' is entered 3 times, on the 3rd time, "duplicate" is printed 2 times. And so on. But not a big deal.
try this:
#include <iostream>
using namespace std;
int main() {
char myAlpha[20];
char input;
cout << "Enter a letter" << endl;
for (int i = 0; i < 20; i++) {
cin >> input;
myAlpha[i] = input;
for (int k = 0; k < i; k++) {
if (myAlpha[k] == input)
cout << "Duplicate" << endl;
}
}
}
With this line:
char myAlpha[20];
The valid indices of that array are from 0 to 19. However, this line:
for (int i= 0; i <= 20; i++) {
Already implies a bug. Change it to this:
for (int i= 0; i < 20; i++) {
Do the same treatment for the inner for loop line: for (int k = 0; k <= 20; k++) {
But... you'll also need to keep track of how many characters have been inserted instead of looping up to 20 again.
So this is closer to what you want:
int main() {
char myAlpha[20];
char input;
cout << "Enter a letter" << endl;
int inserted = 0;
while (inserted < 20) {
cin >> input;
bool duplicate = false;
for (int k = 0; k < inserted; k++) {
if (myAlpha[k] == input) {
cout << "Duplicate" << endl;
duplicate = true;
break; // no point in continuing to look for duplicates once the first one is found
}
}
if (!duplicate) {
myAlpha[inserted] = input;
inserted++;
}
}
}
Even faster and you can avoid the inner for-loop:
int main() {
bool duplicates[256] = {};
char myAlpha[20] = {};
char input;
cout << "Enter a letter" << endl;
int inserted = 0;
while (inserted < 20) {
cin >> input;
bool duplicate = duplicates[(unsigned char)input];
if (duplicate) {
cout << "Duplicate" << endl;
}
else {
myAlpha[inserted] = input;
inserted++;
duplicates[(unsigned char)input] = true;
}
}
}
Related
I am currently writing a task where the user will input a number and it'll output a number of "*" depending on the number. Eg if the user inputted a 5, the answer would be:
*
**
***
****
*****
This is my current code:
#include <iostream>
using namespace std;
int number;
char star = '*';
int main()
{
cout << "Input a number between 1 and 10" << endl;
cin >> number;
for (int i = 0; i < number; i++)
{
for (int j = i; j < number; j++)
{
cout << star;
}
cout << " " << endl;
}
return 0;
}
If the number 5 was inputted, this would output:
*****
****
***
**
*
How would I go about reversing the order so that it is ascending order rather than descending.
You would need to use the for loop in descending instead of ascending order.
Example:
cout << "Input a number between 1 and 10" << endl;
cin >> number;
for (int i = number -1; i >= 0; i--) {
for (int j = i; j < number; j++) {
cout << star;
}
cout << "*" << endl;
}
return 0;
}
You can do that by just reversing the order of the change of i:
#include <iostream>
using namespace std;
int number;
char star = '*';
int main()
{
cout << "Input a number between 1 and 10" << endl;
cin >> number;
//for (int i = 0; i < number; i++)
for (int i = number - 1; i >= 0; i--)
{
for (int j = i; j < number; j++)
{
cout << star;
}
cout << "*" << endl;
}
return 0;
}
(Just how to reverse the order of the change of i is shown. The output of this program is not as expected.)
My preference is using i as the number of stars to print and avoiding using gloval variables and using namespace std;:
#include <iostream>
int main()
{
int number;
char star = '*';
std::cout << "Input a number between 1 and 10" << std::endl;
std::cin >> number;
for (int i = 1; i <= number; i++)
{
for (int j = 0; j < i; j++)
{
std::cout << star;
}
std::cout << std::endl;
}
return 0;
}
Just go from number all the way down instead of up:
for (int i = number; i > 0; i--)
{
for (int j = i; j > 0; j--)
{
cout << star;
}
std::cout << '\n';
}
Instead of j<number use j<i and instead of j=i use j=0:
#include <iostream>
using namespace std;
int number;
char star = '*';
int main()
{
cout << "Input a number between 1 and 10" << endl;
cin >> number;
for (int i = 0; i < number; i++)
{
for (int j = 0; j < i; j++)
{
cout << star;
}
cout << "*" << endl;
}
return 0;
}
there are multiple ways to achieve what you want. You can insert everything inside and array and print the array backwards, insert everything inside an array (starting from last position) and then print it in natural order, you can do it only by using indexes (like i and a lot of other persons did here). I also added a little input check, and put the code in functions for clearness:
#include <iostream>
using namespace std;
int number;
char star = '*';
void version1();
void version2();
int main()
{
cout << "Input a number between 1 and 10" << endl;
cin >> number;
while(number < 1 || number > 10)
{
cout << "I SAID BETWEEN 1 AND 10, IS EASY, RIGHT?" << endl;
cin >> number;
}
version1();
version2();
return 0;
}
void version1()
{
cout <<"Version 1: "<<endl;
for (int i = 0; i < number; i++)
{
for (int j = i; j < number; j++)
{
cout << star;
}
cout << endl;
}
}
void version2()
{
cout << "Version 2: (only by using indexes)" << endl;
int cap_index = 0;
for (int i = 0; i < number; i++)
{
cap_index = i + 1;
for (int j = 0; j < cap_index; j++)
{
cout << star;
}
cout << endl;
}
}
btw this is a more serious (and simple) way to check input:
do
{
cout << "Input a number between 1 and 10" << endl;
cin >> number;
}while(number < 1 || number > 10);
In my case i put it this way:
starting from 0 print '*' up to i + 1 times, this way you have an ascending order print:
first time (from 0 to 1) print '*' -> print once
second time (from 0 to 2) print '*' -> prints twice
and so on up to the inserted number
Obviously this isn't not the best way to do this nor the most elegant, like in nearly every situation there are a lot of possibilities.
ps. i'm not sure, but you have an error in your code, as it prints a '*' more, each time, i don't know how is your output like that
By using a std::string, you can avoid the need of an explicit inner loop.
#include <iostream>
#include <string>
int main()
{
int number;
char star = '*';
std::cout << "Input a number between 1 and 10" << "\n";
std::cin >> number;
for (int i = 0; i < number; i++)
{
std::cout << std::string (i+1, star) << "\n";
}
return 0;
}
Changing the second 'for' loop condition, in your function --
From,
for (int j = i; j < number; j++)
Change it to ,
for (int j = 0; j <= i; j++)
I've been learning C++ for only a couple of months. We had a project that was due about pointers/reference. This is my code below that I submitted. However, My teacher said I didn't include pointers/references in my code. I was certain that I did on line 31-42. I'm having trouble understanding pointers. Please give feedback on what I should do differently.
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
using namespace std;
int main()
{
//Opening File
ifstream cafefile;
cafefile.open("cafeteria.txt");
//Check for errors
if (!cafefile)
{
cout << "cafeteria.txt did not open properly" << endl;
exit(9999);
}
//String & char
string choice;
string array[4][3];
char out;
//Pointers to the food
string food[] { "Cheese Pizza", "Hamburger", "Fish Sticks", "Mystery Meat" };
string *foodptr {food};
//Set yes & no to 4 array
int yes[4]{ 0 };
int no[4]{ 0 };
//pointer for integer Yes / NO
int* yesptr{ yes };
int* noptr{ no };
//Counters of Likes & Dislikes set = 0
int like = {0};
int dislike = {0};
for (int i = 0; i < 4; i++)
{
//Reopen the file
ifstream file("cafeteria.txt");
while (getline(file, choice))
{
istringstream pick(choice); //istringstream is input stream class, which operates on string
getline(pick, choice, '\t');
if (foodptr[i] == choice)
{
pick >> choice;
if (choice == "Y")
like++; //increment
else if (choice == "N")
dislike++; //increment
}
}
//Setting the yes = like
yesptr[i] = like;
noptr[i] = dislike;
//Set to 0
like = 0;
dislike = 0;
}
for (int m = 0; m < 4; m++)
{
array[m][0] = foodptr[m];
}
for (int j = 0; j < 4; j++)
{
array[j][1] = to_string(yesptr[j]);
}
for (int i = 0; i < 4; i++)
{
array[i][2] = to_string(noptr[i]);
}
//Display of the Program
cout << "School Cafeteria Survey!" << endl;
cout << endl;
cout << "Food Item" << "\t" << "Like" << "\t" << "Dislike" << endl; //Gives the tab space Horizontally in your output
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 3; j++)
{
cout << array[i][j] << "\t";
}
cout << endl;
}
//Background color, making it unique
system("color 6");
//Exit the Prgram
cout << endl;
cout << "Please enter 'E' to exit!";
cin >> out;
if (out == 'e' || out == 'E')
{
exit(0);
}
system("pause"); //pause the program
return 0;
}
Please provide solutions on what I should fix.
It would be better if you create your arrays dynamically i.e. make the 2D array dynamically using pointers
string **array;
array = new int *[4];
for(int i=0; i<4; i++){
array[i] = new int[3];
}
Other than this, your teacher must have wanted your to access these array not using indexing, but rather by using pointers and references. This means that you shouldn't access arrays using yesptr[i] but rather by using *(yesptr + i).
So for e.g. if you are in a loop do the following
for (int m = 0; m < 4; m++)
{
*(*(array+m)+0) = *(foodptr+m);
}
I am stuck on what to do next... The program is suppose to check to see if entered Zero-One Matrix is an Equivalence relation (transitive, symmetric, and reflexive) or not. I am still new to C++ (started this semester). I know how to create the matrix using vector but not on how to check if it is equivalence relation or not..
I assume I need to use boolean function but I'm stuck on what I need to put in as an argument or if this is correct. My original thought was... so for symmetric it will look like (which I know this goes after #include and beofre int main(). Any help would be awesome.
bool isSymmetric(vector<int> &vect, int Value)
{
for (int i = 0; i < Value; i++)
for (int j = 0; j < Value; j++)
if (vect[i][j] != vect[j][i])
return false;
return true;
}
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector< vector<int> > vec;
cout << "NxN matrix N: ";
int Value;
cin >> Value;
cout << Value << "x" << Value << " matrix\n";
for (int i = 0; i < Value; i++) {
vector<int> row;
for (int j = 0; j < Value; j++) {
cout << "Enter a number (0 or 1): ";
int User_num;
cin >> User_num;
while (User_num != 0 && User_num != 1) {
cout << "Invalid Entry! Enter 0 or 1!\n";
cout << "Enter a number (0 or 1): ";
cin >> User_num;
}
row.push_back(User_num);
}
vec.push_back(row);
}
cout << endl;
for (int i = 0; i < Value; i++) {
for (int j = 0; j < Value; j++) {
cout << vec[i][j] << " ";
}
cout << endl;
}
cout << endl;
system("pause");
return 0;
}
I'm picking up on C++ recently and is trying to code a program which prompts for names for a defined no. of times and inserts each of the input into an array of size-5. The problem happened when I tried to run the following code, my counter, i increases according to the no of len the user input. Why is that so?
#include <iostream>
using namespace std;
int main(){
const int SIZE = 5;
char name[SIZE];
int i;
for (i = 0; i < SIZE; i++){
if (strlen(name) <= 50) {
cout << "Enter a name: \n";
cin >> name[i];
}
}
for (i = 0; i < SIZE; i++){
cout << name[i] << endl;
}
return 0;
}
Output:
if (strlen(name) <= 50) {
You should not call strlen on array which is not initialized.
Use array of strings otherwise
cout << name[i] << endl;
refers to i-th character, not entire string. Or if you want to go with char arrays, you'd need a two dimensional array.
I thing what you indended to do was :
#include <iostream>
using namespace std;
int main(){
const int SIZE = 5;
string names[SIZE];
int i;
for (i = 0; i < SIZE; i++){
cout << "Enter a name: \n";
string name;
cin>>name;
if (strlen(name) <= 50) {
cin >> names[i];
}
}
for (i = 0; i < SIZE; i++){
cout << name[i] << endl;
}
return 0;
}
UNTESTED
The second for loop, which does the output, does this in single characters, incrementing i each time.
To output the string all at once assign a string pointer to name[0] and send that to cout.
I need help with getting this users input of an integer and retrieving the even numbers and displaying them with spaces.I already have the input processed into an array and have it reversed (thanks to stackoverflow) now need to extract the even numbers from the array and display them.
#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;
int evenNumbers(char even[], int num[], int indexing[]);
int main()
{
char integers[5];
int numbers[5];
int even[5] = {0,2,4,6,8};
int evens;
cout << "Please enter an integer and press <ENTER>: " << endl;
for (int j = 0; j < 5; j++)
cin >> integers[j];
for (int j = 0; j < 5; j++)
{
numbers[j]= integers[j] - '0';
}
cout << endl;
for (int j = 5; j > 0; j--)
{
cout << integers[j - 1] << " ";
}
cout << endl;
//having problems finding the even numbers and displaying the even numbers
//from the users input of integers, i have only learned how to display the
//subscript by a linear search
evens = evenNumbers(integers, numbers, even);
if (evens == -1)
cout << "There are no even numbers" << endl;
else
{
cout << "The even numbers are: " << (evens + 1) << endl;
}
system("pause");
return 0;
}
int evenNumbers(char even[], int num[], int indexing[])
{
int index = 0;
int position = -1;
bool found = false;
for (int j = 0; j < 5; j++)
{
num[j]= even[j] - '0';
}
while (index < 5)
{
if (num[index] == indexing[index])
{
found = true;
position = index;
}
index++;
}
return position;
}
If you want to display the even numbers from the array integers you can use a simple for loop and if statement:
for(int i = 4; i >= 0; i--)
{
if(integers[i] % 2 == 0)
cout << integers[i] << " ";
}
Your approach is all wrong, you can't detect even numbers by searching a list, you need a mathematical test for evenness. Write a function called is_even which tests one number and returns true if it is even and false if it is not. Then you can use that function, very simply, like this
for (int j = 0; j < 5; j++)
{
if (is_even(integers[j]))
cout << integers[j] << " ";
}
cout << endl;
Now you just need to write the is_even function.
void evennumbers(int num[])
{
for(int i=0;i<5;i++)
{
if(num[i]%2==0)
cout<<num[i]<<" ";
}
}
And avoid taking input to char what if user enters a number with more than one digit
#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;
void validNum(char valid[]);
void reverseNum(char rev[], int num2[]);
void evenNumbers(char even[], int num3[]);
void oddNumbers(char odd[], int num4[]);
int main()
{
char integer[5];
int number[5];
cout << "Your number is: ";
validNum(integer);
cout << "Your number in reverse is: ";
reverseNum(integer, number);
cout << "Even numbers: ";
evenNumbers(integer, number);
cout << endl;
cout << "Odd numbers: ";
oddNumbers(integer, number);
cout << endl;
system("pause");
return 0;
}
void validNum(char valid[])
{
char ch;
cout << "Please enter an integer and press <ENTER>: " << endl;
ch = cin.get;
while (ch < 0 || ch >= 'A' && ch <= 'Z' || ch >= 'a' && ch <= 'z')
{
cout << "ERROR: Please enter a positive integer and press <ENTER>: ";
for (int i = 0; i < 5; i++)
cin >> valid[i];
}
for (int j = 0; j < 5; j++)
{
cout << valid[j] - '0';
}
}
void reverseNum(char rev[], int num2[])
{
for (int j = 0; j < 5; j++)
{
num2[j]= rev[j] - '0';
}
cout << endl;
for (int j = 5; j > 0; j--)
{
cout << rev[j - 1]<< " ";
}
cout << endl;
}
void evenNumbers(char even[], int num3[])
{
for (int i = 0; i < 5; i++)
{
if (even[i] % 2 == 0)
{
cout << num3[i] << " ";
}
}
}
void oddNumbers(char odd[], int num4[])
{
for (int i = 0; i < 5; i++)
{
if (odd[i] % 2 == 1)
{
cout << num4[i] << " ";
}
}
}