I used a do while loop to ask user to enter integer as long as its not 0 or it will exit the program. I'm stuck on how to store every user input into the dynamically allocated array.
#include <iostream>
using namespace std;
int main() {
int *A;
A= new int();
int n;
do{
cout<<"Enter integer: "<<endl;
cin>>n;
cout<< *A + n << endl;
}while(n!=0);
return 0;
}
You are allocating a single int, not an array of ints.
Also, even if you were allocating an array, a statement like *A + n does not add n to the array. It dereferences A to access the value of the 1st int in the array, and then adds n to that value.
Try something more like this instead:
#include <iostream>
using namespace std;
int main() {
int *A = nullptr;
int count = 0, n;
do{
cout << "Enter integer: " << endl;
cin >> n;
if (n == 0) break;
int *newA = new int[count+1];
for(int i = 0; i < count; ++i) newA[i] = A[i];
newA[count] = n;
delete[] A;
A = newA;
++count;
cout << A[count-1] << endl;
}
while (true);
delete[] A;
return 0;
}
Alternatively, try to avoid reallocating the array on every input, eg:
#include <iostream>
using namespace std;
int main() {
int *A = new int[5];
int count = 0, cap = 5, n;
do{
cout << "Enter integer: " << endl;
cin >> n;
if (n == 0) break;
if (count == cap)
{
int newCap = cap * 1.5;
int *newA = new int[newCap];
for(int i = 0; i < count; ++i) newA[i] = A[i];
delete[] A;
A = newA;
cap = newCap;
}
A[count] = n;
++count;
cout << A[count-1] << endl;
}
while (true);
delete[] A;
return 0;
}
That being said, a better option is to use a std::vector, which will handle the dynamic memory for you, eg:
#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<int> A;
int n;
do{
cout << "Enter integer: " << endl;
cin >> n;
if (n == 0) break;
A.push_back(n);
cout << A.back() << endl;
}
while (true);
return 0;
}
I am trying to input data to an array and then print them by using a function but I am not sure how to organize the code.
#include <iostream>
using namespace std;
void showGrade(double grade[], int size);
int main()
{
double grade[];
int size;
for (int i = 0; i < size; i++)
{
cout << "Please enter the number of grade" << endl;
cin >> size;
}
showGrade(grade, size);
return 0;
}
void showGrade(double grade[], int size) //How many grade we have
{
for (int counter = 0; counter < size; counter++)
{
cout << "Please enter your grades: " << endl;
cin >> grade[counter];
cout << "Here are your grades: " << endl;
}
}
I Expect to see how many grades I input and then show them.
UPDATE 8/28/19
I figured out how to do it in main function successfully. But what I really want is to put them in a seperate function. My new codes have error at the function call which is type name is not allowed and expected a ')'. How do I make it work?
#include <iostream>
using namespace std;
void showGrades(double ar[], int size);
int main()
{
double ar[20];
int size;
showGrades(double ar[size], int size);
system("pause");
return 0;
}
void showGrades(double ar[], int size) {
cout << "Please enter the number of grade "; // array size
cin >> size;
cout << "Please enter your grades " << endl;
for (int i = 0; i < size; i++) {
cin >> ar[i];
}
cout << "The grades you entered are: " << endl;
for (int i = 0; i < size; i++) {
cout << ar[i] << endl;
}
}
First of all, you need to use the standard container
std::vector
instead of the double grade[];, since you want a variable-length
array as per user input.
Secondly, you are using un-initialized size variable in
for (int i = 0; i < size; i++)
hence it will be initialized with a garbage value. There you need no for-loop
A good starting would be:
#include <iostream>
#include <vector> // std::vector
void showGrade(std::vector<double>& grade)
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -> pass the vector by ref, as the grades should be inseted to the it
{
// the logic
}
int main()
{
int size;
std::cout << "Please enter the number of grade" << endl;
std::cin >> size;
std::vector<double> grade;
grade.reserve(size); // reserve memory for unwanted re-allocations
showGrade(grade);
return 0;
}
I leave it to you to complete, after reading about the std::vector more.
Also, do not practice with using namespace std;. Read more:
Why is "using namespace std;" considered bad practice?
this is not a valid C++ code:
double grade[];
You can use std::vector:
std::vector<double> grade;
To insert a grade to the vector you can use grade.push_back(someGrade);
I'm trying to write a program that will have a user input size for an array, and then take values into that array. I initially tried
int sz = 51;
double Arr[sz];
Which led to compilation errors. Apparently dynamic allocation of the variable has to happen, and I'd rather avoid that if possible. So I modified my code (current state as shown below) which now only throws "expected primary-expression before ']' token". Is there a way to fix this and I'm just not seeing it, or do I need to use dynamic allocation?
Thanks for your time!
#include <iostream>
#include <iomanip> //for setprecision
using namespace std;
int sz = 51;
double n=0;
double Arr[0];
void get_input(double Arr[], int &sz){ //gets input
do{
cout<< "Enter size: "<< endl;
cin>> sz;
if (sz<0 || sz>50){
cout<< "Invalid size, enter a value between 0 and 50"<<endl;
}
}while(sz<0 || sz>50);
for( int i=0; i<sz; i++){
cin>> Arr[i];
}
}
double calcSum( double Arr[], int sz){ //finds sum
for(int i=0; i<sz; i++){
n+= Arr[i];
}
return(n);
}
void printArray(double Arr[], int sz){ //prints array elements
for(int i=0; i<sz; i++){
cout<< Arr[i]<< setprecision(2)<<" ";
if(i%7 == 0)
cout<< endl;
}
}
int main()
{
double Arr[sz];
get_input(Arr[], sz); //error here
printArray(Arr[], sz); //error here
return 0;
}
VLAs (e.g. Arr[sz]) are only supported as extensions in C++. They aren't part of the official language standard. You should use std::vector instead.
Just use a std::vector, there's a standard library in C++ for this reason.
Demo:
notes: you don't need the globals (they are shadowed by the locals and you pass them by reference anyways)
Live On Coliru
#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;
using array_t = std::vector<double>;
void get_input(array_t& Arr) { // gets input
size_t sz = 51; // unsigned types cannot be negative
do {
cout << "Enter size: " << endl;
cin >> sz;
if (sz > 50) {
cout << "Invalid size, enter a value between 0 and 50" << endl;
}
} while (sz > 50);
for (size_t i = 0; i < sz; ++i) {
double v;
if (cin >> v)
Arr.push_back(v);
else
std::cerr << "Error reading input\n";
}
//assert(sz = Arr.size());
}
double calcSum(array_t const& Arr) { // finds sum
double n = 0;
for (size_t i = 0; i < Arr.size(); ++i) {
n += Arr[i];
}
return n;
}
void printArray(array_t const& Arr) { // prints array elements
for (size_t i = 0; i < Arr.size(); ++i) {
cout << Arr[i] << setprecision(2) << " ";
if (i % 7 == 6)
cout << endl;
}
}
int main() {
array_t Arr;
get_input(Arr);
printArray(Arr);
std::cout << "\nSum: " << calcSum(Arr) << "\n";
}
When entering 3 1 2 3 you get:
Enter size: 3
1 2 3
1 2 3
Sum: 6
Here is what I have come up with so far... I am so close with literally 1 error left for it to compile.
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
const int SIZE = 3;
bool equals(const int m1[][SIZE], const int m2[][SIZE])
{
bool identical = true;
for (int i=0; i < SIZE && identical; i++ )
{
if (m1[i] != m2[i]){
identical = false;
}
}
return identical = true;
}
void printArray(const int m1[], int size)
{
for (int i = 0; i < size; i++)
cout << m1[i] << " ";
}
void printArray2(const int m2[], int size) //not sure if I need this 2nd
{ //void
for (int i = 0; i < size; i++)
cout << m2[i] << " ";
}
int main()
{
string input1, input2;
int const SIZE = 3;
double inputnumber;
int m2[SIZE];
int m1[SIZE];
cout << "Please enter the first array: " << endl;
getline(cin, input1);
stringstream ss (input1);
ss >> inputnumber;
cout << "Please enter the second array: " << endl;
getline(cin, input2);
stringstream si (input2);
si>>inputnumber;
for (int i=0; i< inputnumber ; ++i) {
ss >> m1[i];}
if (equals(m1, SIZE)){
cout << "The two arrays are identical ! ";
}
else{
cout << "The two arrays are NOT identical !";
}
cout << endl;
return 0;
}
Or at least I think that I am close... any help is much appreciated.
My current error is coming up on the IF statement in the main function. I could have more mistakes as I am very very new to C++. Like I said please help me out if you can.
If you just want code here it is , but if you want to practice I recommend you to implement error checking(incorrect format) in this code and to change the loops in my code into functions.
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main()
{
string inp;
cout<<"Please enter an array of numbers in the following form\n"
"(where N's are any numbers) :\n"
"[N N N\nN N N\nN N N"<<endl;
double m1[3][3],m2[3][3];
for(short i=0;i<3;i++){
cout<<"> ";
if(i==0) cout<<"[ ";
getline(cin,inp);
stringstream inps(inp);
for(short j=0;j<3;j++){
inps>>m1[i][j];
}
}// Get the first array
cout<<"Now enter the second array :\n";
for(short i=0;i<3;i++){
cout<<"> ";
if(i==0) cout<<"[ ";
getline(cin,inp);
stringstream inps(inp);
for(short j=0;j<3;j++){
inps>>m2[i][j];
}
}// Get the second one
bool not_equal=false;
for(short i=0; i<3 && !not_equal ;i++)
for(short j=0; j<3 && !not_equal ;j++)
if(m1[i][j]!=m2[i][j])
not_equal=true;// Test equality
if(not_equal)
cout<<"The two arrays you entered are not equal !!"<<endl;
else
cout<<"The two arrays you entered are EQUAL ."<<endl;
return 0;
}
#include <iostream>
using namespace std;
int main()
{
int size = 3;
int m2[size][size];
int m1[size][size];
cout << "Please enter the first array: " << endl;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
cin >> m1[i][j];
}
}
cout << "Please enter the second array: " << endl;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
cin >> m2[i][j];
}
}
int flag=1;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
if(m2[i][j]!=m1[i][j])
{
flag=0;
}
}
}
if(flag==1)
{
cout <<"SAME"<<endl;
}
else if(flag==0)
{
cout <<"NOT SAME"<<endl;
}
return 0;
}
I have a program that sorted arrays how can i save in text file?
for example: the sorted arrays is: 1, 2, 3, 4, 5.
how can i save in text file named. Sorted elements".
I've tried many ways but the sorted array wouldn't save in text file.
I am a newbie so I find it difficult.
here is my code.
#include <iostream>
using namespace std;
int main() {
cout << "Enter number of element:";
int n; cin >> n;
int a[n];
for(int i=0;i<n;i++)
{
cout << "element number " << (i+1) << " : ";
cin >> a[i];
}
int e=1, d=3;
int i, j, k, m, digit, row, col;
int length = sizeof(a)/sizeof(int);
int bmat[length][10];
int c[10];
for(m=1;m<=d;m++)
{
for(i=0;i<10;i++)
{
c[i]=-1;
}
for(i=0;i<length;i++)
{
digit=(a[i]/e)%10;
c[digit]++;
row=c[digit];
col=digit;
bmat[row][col]=a[i];
}
k=-1;
for(i=0;i<10;i++)
{
if(c[i]!=-1)
{
for(j=0;j<=c[i];j++)
{
k++;
a[k]=bmat[j][i];
}
}
}
e=e*10;
}
cout << endl;
cout << "Sorted array:" << endl;
for(int i=0;i<n;i++)
{
cout << a[i] << " , ";
}
cout << endl;
system("pause");
return 0;
}
//Use this code
#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
using namespace std;
int main()
{
int n = 0;
cout << "Enter number of element:";
cin >> n;
//Data Structure
std::vector<int> list;
//push back element in vector
for(register int i=0;i<n;++i)
list.push_back(rand()%10 + 1);
//do shuffling before sorting because rand() generates increasing order number
std::random_shuffle(list.begin(),list.end());
std::sort(list.begin(),list.end());
ofstream textfile;
textfile.open ("E:\\example.txt");
for(size_t i= 0;i<list.size();++i)
textfile << list[i] <<" ";
textfile.close();
}
If you can write the sorted array to std::cout, then you can write it to a file. In C++, the console is the same as a file.
Put this at the end of main:
cout << "Sorted array:" << endl;
print_array( std::cout, a, n ); // Show the results to the user.
std::ofstream save( "array.txt" ); // Open a new file (or overwrite).
print_array( save, a, n ); // Save the results for later.
system("pause");
return 0;
}
and put the printing code in a new function, which may be defined before main:
void print_array( std::ostream & s, int * a, int n ) {
for(int i=0;i<n;i++)
{
s << a[i] << " , ";
}
s << endl;
}
#include<iostream>
#include<fstream>
using namespace std;
int compare(int, int);
void sort(int[], const int);
int compare(int x, int y){
return(x > y);
}
void swap(int *x, int *y){
int temp;
temp = *x;
*x = *y;
*y = temp;
}
void display(int array[], int n){
for (int i = 0; i<n; i++) {
cout << array[i] << " ";
}
cout << endl;
}
void writeToFile(int array[], int n){
ofstream myfile;
myfile.open("example.txt");
for (int i = 0; i<n; i++) {
myfile << array[i];
if (i != n - 1){
myfile << ", ";
}
}
myfile.close();
}
void sort(int table[], const int n) {
for (int i = 0; i < n; i++){
for (int j = 0; j < n - 1; j++) {
if (compare(table[j], table[j + 1]))
swap(&table[j], &table[j + 1]);
}
}
}
int main(){
int quantity;
int* tab;
ofstream outfile;
cout << "Enter number of element: ";
cin >> quantity;
tab = new int[quantity];
cout << "Element:\n\n" << endl;
for (int i = 0; i < quantity; i++){
int x = i;
cout << "#" << ++x << ":";
cin >> tab[i];
}
sort(tab, quantity);
cout << "The Sorted Elements are: ";
display(tab, quantity);
writeToFile(tab, quantity);
cout << endl;
getchar();
getchar();
//system("pause");
return 0;
}
in short, add this block to your code:
ofstream myfile;
myfile.open("example.txt");
for (int i = 0; i<n; i++) {
myfile << array[i];
if (i != n - 1){
myfile << ", ";
}
}
myfile.close();
You can use C++ fstream class, since you want to output, you can use ofstream here. You should just replace some "cout" with ofstream instance:
At the beginning of the code state it:
ofstream ofs("./sorted_elem.txt", ofstream::out);
When want to output:
ofs << "Sorted array:" << endl;
for(int i=0;i<n;i++)
{
ofs << a[i] << " , ";
}
ofs << endl;
In C++ you really want to use std::vector or some other nice container for storing arrays of numbers. For writing an array to file you need to open the file and individually write each element to the file (all untested).
#include <fstream>
int main()
{
std::ofstream fp("output.txt");
int data[5]; // todo: fill
for (unsitned i = 0; i < 5; ++i)
{
fp << data[i] << ' ';
}
}
And to read again:
#include <fstream>
int main()
{
std::ifstream fp("output.txt");
// todo: Determine the size of the array or guess it (don't guess it!)
unsigned array_size = 5;
int data[array_size];
int n = 0;
while (fp.good() && n < array_size) fp >> data[n++];
}
But because we are using C++, we can use std::vector:
#include <fstream>
#include <vector>
int main()
{
std::vector<int> me(5); // todo: fill
std::ofstream fp("output.txt");
for (size_t i = 0; i < me.size(); ++i) fp << me[i] << ' ';
// C++11: for (int d : me) fp << d << ' ';
}
And,
#include <fstream>
#include <vector>
int main()
{
std::ifstream fp("output.txt");
std::vector<int> data;
double buf;
while (fp >> buf) data.push_back(buf); // no longer need to guess
}
I think, the copy option was not demonstrated here so far.
Please check this code. (Assuming your vector is ready to use, I've skipped it).
The example uses a C-array and a vector. Please use the later in your code whenever possible. But however, for copy-function both work:
#include <iostream>
#include <iterator>
#include <vector>
#include <algorithm>
#include <fstream>
int main () {
int a[10]={0,1,2,3,4,5,6,7,8,9};
std::vector<int> v; for (int i=0; i<10; ++i)v.push_back(i*10); //0, 10, 20,...
std::ofstream fs_a( "c:/temp/out_a.txt" );
//store space separated
std::copy ( a, a+sizeof(a)/sizeof(a[0]), std::ostream_iterator<int>( fs_a, " ") );
//store coma-separated, as one-liner
std::copy ( v.begin(), v.end() ), std::ostream_iterator<int>( std::ofstream( "c:/temp/out_v.txt" ), ",") );
return 0;
}