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Every time I run this code in Visual Studio 2015 it shows the error identifier "treasureLocation" is undefined... what am I doing wrong?
int main()
{
int gridSize [2];
int gridX = 0;
int gridY = 0;
int treasureLoaction[2];
int end;
std :: cout << "what size grid would you like to play on?" << std :: endl;
std :: cin >> gridSize [1];
std :: cin >> gridSize [2];
treasureLocation[1] = rand() % gridSize[1] + 1;
treasureLocation[2] = rand() % gridSize[2] + 1;
while (gridY < gridSize[2]) {
gridY++;
while (gridX < gridSize[1]) {
std::cout << "* ";
gridX++;
}
std::cout << "" << std::endl;
gridX = 0;
};
std::cout << treasureLoaction;
std::cin >> end;
return 0;
}
There is a typo
int treasureLoaction[2];
^^^^^^^^
Take into account that if an array has n elements then the valid range of indices is [0, n-1]
And this statement
std::cout << treasureLoaction;
does not outputs the elements of the array as you might think.
You could do it in a loop as for example
for ( int x : treasureLocation ) std::cout << x << ' ';
std::cout << std::endl;
Try iterating through the array to print its contents like this
for (int i = 0; i < your array length; i++) cout << array[i];
unless you are trying to print the address, and it also looks like you have a spelling error in treasureLoaction.
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int n;
cin >> n; cin.ignore();
for(int i = 1; i < 11; i++){
cout << i * n << " ";// stop printing space at the end number
}
Desired output-> "1 2 3 4 5 6 7 8 9 10"
The standard approach is to use a boolean variable, which is one time either true or false, then print a space or not, depending on the boolean, and set the boolen to a new value.
Often the output of the space in the loop is done first and then then value.
Example:
bool printSpace = false;
for(int i = 1; i < 11; ++i) {
if (printSpace) std::cout << ' ';
printSpace = true;
std::cout << i * n;
}
You could also use std::exchange for flipping the bool. Please read here.
Then you could do something like the below:
#include <iostream>
#include <vector>
#include <utility>
int main() {
std::vector data{1,2,3,4};
bool showComma{};
for (const int i: data)
std::cout << (std::exchange(showComma, true) ? "," : "") << i;
}
And the super high sophisticated stuff will be done with the std::ostream_joiner.
Reade here for an example. But, unfortunately this is not available for many installations.
A simple approach is the following
for( int i = 0; i < 10; i++){
if ( i ) cout << ' ';
cout << ( i + 1 ) * n;
}
or
for( int i = 1; i < 11; i++){
if ( i != 1 ) cout << ' ';
cout << i * n;
}
One-liner:
cout << (i > 1 ? " " : "") << i * n;
Note: I prefer the "prefix" form because the starting value is easier to know than the ending one (>1 vs. >9).
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I am a beginner, and I am trying to learn C++.
For now, all I am trying to do is input 3 numbers, and print them back.
#include <iostream>
using namespace std;
int main(){
int n[2];
cout << "Enter three numbers" << endl;
for (int j = 0; j <= 2; j++){
cin >> n[j];
}
cout << "Debug " << n[2] << endl;
cout << endl;
for (int i = 0; i <= 2; i++){
cout << n[i] << "\t" << i << endl;
}
return 0;
}
Every time I print them, the last value of the array is modified, and I cannot figure out why! For a test input 6,7,8, the output is in the image below.
This for
for (int j=0;j<=2;j++){
cin>>n[j];
}
expects that the array has at least three elements with indices in the range [0, 2].
However you declared an array with two elements
int n[2];
If you are going to input three elements then the array should be defined as
int n[3];
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I'm new to programming and i have problem with some items
i would appreciate any help
first i started initializing the vector as followed but i couldn't end the loop with Ctrl+Z
#include "stdafx.h"
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
vector <double> temps;
double temp;
cout << "Enter a sequence of tempreatures : " << "\n" ;
while (cin >> temp){
temps.push_back(temp);
}
double sum = 0;
for (int i = 0; i< temps.size(); ++i)
sum += temps[i];
cout << "Mean temprature : " << sum / temps.size() << "\n";
sort(temps.begin(), temps.end());
cout << "Median temprature : " << temps[temps.size() / 2];
then i changed the while into this format :
cout << "ENter a sequence of tempreatures ending in 1500 : " << "\n" ;
while (cin >> temp){
if (temp == 1500)
break;
temps.push_back(temp);
}
now i have this error
"vector subscript out of range"
apparently break does not work properly here
what should i do?
Your issue is in the check condition of for loop.
for (int i = 0; i, temps.size(); ++i)
sum += temps[i];
It should be
for (int i = 0; i < temps.size(); ++i)
i, temps.size() will evaluate and then ignore the part before , and are left with temps.size() as check condition which will always be greater than 0 if you push_back at least one element and your loop will never end.You might want to read how ,(comma) works.
If you switch to std::getline into a string instead of std::cin into a double, you can check whether the input is empty:
std::string input;
std::getline(std::cin, input);
while (!input.empty()){
temps.push_back(atof(input.c_str()));
std::getline(std::cin, input);
}
If you also fix the for-loop as mentioned by Gaurav Sehgal, it works fine (Enter all numbers then hit enter without any input).
If you are on windows then you have to do
CTRL + Z
If you are on Unix based(Linux/Mac) then you have to do
CTRL + D
This will give the end of file signal and you will be able to break the loop
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int main()
{
vector<int>numbers;
int numb = 0;
int i = 0;
int j = i - 1;
while (cin >> numb)
{
if (numb == numbers[j]) HERE IS THE PROBLEM!*
{
cout << "Numbers repeated\n";
}
numbers.push_back(numb);
cout << "numbers[" << i << "] = " << numbers[i] << endl;
++i;
}
/*** I don't understand why a exception, run time error, break or whatever it names.....................................................
On the first iteration through the loop, j is -1. Accessing numbers[-1] is undefined behavior because the index is outside the bounds of the vector.
Indeed, accessing any index is out of bounds until you put something in the vector, so you cannot index numbers at all until you have called push_back on it at least once.
This code will display the message if the user enters a number already in the vector:
while (cin >> numb) {
vector<int>::iterator found = std::find(numbers.begin(), numbers.end(), numb);
if (found == numbers.end()) {
cout << "Numbers repeated" << endl;
}
// If you don't want duplicate numbers in the vector, move this statement
// into an "else" block on the last "if" block.
numbers.push_back(numb);
}
This code on the other hand will only display the message when a number was the same as the last number entered, that is, if sequential numbers are the same:
while (cin >> numb) {
if (!numbers.empty() && numb == numbers.back()) {
cout << "Numbers repeated" << endl;
}
numbers.push_back(numb);
}
You need to initialize your numbers vector with initial data, or check to make sure j is withing in vector size. A vector is essentially an array, and like any array, you cannot go out of bounds.
if (j < numbers.size() && numb == numbers[j]) HERE IS THE PROBLEM!*
{
cout << "Numbers repeated\n";
}
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I am trying to get the greatest value from the array and its index number also by using a function maxin but my logic somehow isn't working?
#include <iostream>
#include <conio.h>
#include <proceass.h>
void maxin(double[], int);
void main()
{
const int k = 10;
int l = 0;
double num[k];
for (int j = 0; j < k; j++)
{
cout << "Enter the number " << j + 1 << " = ";
cin >> num[j];
if (cin.fail())
{
cout << "Wrong data entered " << "\nTry again";
getch();
exit(0);
}
}
maxin(num, l);
cout << "The Greatest number is = " << num;
cout << "\nIt is " << l << "th number";
getch();
}
void maxin(double k[], int p)
{
int l, s;
l = 10;
s = 0;
double m;
for (int n = 0; n < l; n++)
{
if (k[s] > k[n++])
{
m = k[n];
}
else
{
m = k[n++];
s = ++;
}
}
p = s;
k[s] = m;
}
Your maxin function is invoking Undefined Behavior on your program for causing access to areas beyond the bounds of the array k. This happens because not only is n incremented in the for loop statement, but again in the if statement which is evaluated on each iteration as well. This also happens in the else statement, which is another case of the problem.
When n is 1 less than l, n++ will be >= l, and subsequently dereferencing that address, k[n++], will cause Undefined Behavior. After that, anything can happen to your program, including valid or invalid side effects.
When finding the maximum/minimum value in an array, a variable is usually set to an arbitrary value in the array (typically the first index), and then iteration is performed to check if any other value in the array is smaller/larger than that variable. When that condition passes, the variable is set to the new value in the array.
Furthermore, since you said you needed to set the variable to the index at which the largest value was found, it is necessary that you pass p by reference.
The STL approach:
vector< double > v = {1,2,3,4,5};
auto maxElemIter = std::max_element(begin(v), end(v));
cout << "Max is: " << *maxElemIter;
cout << ", at index: " << distance(begin(v), maxElemIter) << endl;
(I know, this is a cruel suggestion, given code as stated in question above...)