Stack around the variable is corrupted - c++

I have what seems like a pretty simple, beginner question that I must be missing something obvious. I am just trying to prompt the user to input a 4 digit number and then take in the input as an array, splitting up the digits to be by themselves. I thought it hade something to do with "cin >> input[4]" I just can't seem to get the right answer.
int main()
{
int input[4]; //number entered by user
cout << "Please enter a combination to try for, or 0 for a random value: " << endl;
cin >> input[4];
}
When I go to run it, I get an error message "Stack around the variable was corrupted.
I tried looking at similar examples in other questions but I just can't seem to get it right. I need the input as one 4 digit number and then split it up to a 4 position array.
If anyone could help I would greatly appreciate it.

Your array is of size 4, so elements have indicies 0 .. 3; input[4] is located behind the end of your array so you are attemping to modify memory not allocated or allocated for other stuff.
This will work for you:
cin >> input[0];
cin >> input[1];
cin >> input[2];
cin >> input[3];
You do not need an arry to input 4 digit number.
int in;
int input[4];
cin >> in;
if(in>9999 || in < 1000) {
out << "specify 4 digit number" << endl;
return;
}
input[0] = in%1000;
input[1] = (in-1000*input[0])%100;
input[2] = (in-1000*input[0]-100*input[1])%10;
input[3] = in-1000*input[0]-100*input[1]-input[2]*10;

The problem is that you are trying to read in a character that does not exist (the one at index 4).If you declare input as int input[4];, then it doesn't have any characters at index 4; only indices 0...3 are valid.
Perhaps you should just use an std::string and std::getline(), and you could then parse the user input to integers however you like. Or you can try
std::cin >> input[0] >> input[1] >> input[2] >> input[3];
if you can live with the constraint that the numbers must be whitespace-separated.

This includes a small bit of error checking:
int n = 0;
while( n < 1000 || n >= 10000 ) // check read integer fits desired criteria
{
cout << "enter 4 digit number: ";
cin >> n; // read the input as one integer (likely 10 digit support)
if( !cin.good() ) // check for problems reading the int
cin.clear(); // fix cin to make it useable again
while(cin.get() != '\n'); // make sure entire entered line is read
}
int arr[4]; // holder for desired "broken up" integer
for( int i=0, place=1; i<4; ++i, place *= 10 )
arr[i] = (n / place) % 10; // get n's place for each slot in array.
cout << arr[3] << " " << arr[2] << " " << arr[1] << " " << arr[0] << endl;

Related

after push_back cin doesnt work

I have a problem with this code:
int main()
{
int x, sum = 0, how_many;
vector<int> v;
cout << "Write few numbers (write a letter if u want to end)\n";
while (cin >> x)
{
v.push_back(x);
}
cout << "How many of those first numbers do u want to sum up?" << endl;
cin >> how_many;
for (int i = 0; i < how_many; ++i)
{
sum += v[i];
}
cout << "The sum of them is " << sum;
return 0;
}
The problem is that console doesn't let me even write sth into how_many and error occurs. When I put lines 6 and 7 before cout << "Write few..." it all works perfectly. Can someone tell me why is that happening?
The loop ends when cin fails to convert the input into an integer, which leaves cin in a bad state. It also still contains final line of input. Any further input will fail, unless you clear the bad state:
cin.clear(); // clear the error state
cin.ignore(-1); // ignore any input still in the stream
(If you like verbosity, you could specify std::numeric_limits<std::stream_size>::max(), rather than relying on the conversion of -1 to the maximum value of an unsigned type).
You need to clear the cin error state because you ended the int vector read operation by an error.
cin.clear();
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');

do while loops can't have two cin statements?

I'm just following a simple c++ tutorial on do/while loops and i seem to have copied exactly what was written in the tutorial but i'm not yielding the same results. This is my code:
int main()
{
int c=0;
int i=0;
int str;
do
{
cout << "Enter a num: \n";
cin >> i;
c = c + i;
cout << "Do you wan't to enter another num? y/n: \n";
cin >> str;
} while (c < 15);
cout << "The sum of the numbers are: " << c << endl;
system("pause");
return (0);
}
Right now, after 1 iteration, the loop just runs without asking for my inputs again and only calculating the sum with my first initial input for i.
However if i remove the second pair of cout/cin statements, the program works fine..
can someone spot my error please? thank you!
After you read the string with your cin >> str;, there's still a new-line sitting in the input buffer. When you execute cin >> i; in the next iteration, it reads the newline as if you just pressed enter without entering a number, so it doesn't wait for you to enter anything.
The usual cure is to put something like cin.ignore(100, '\n'); after you read the string. The 100 is more or less arbitrary -- it just limits the number of characters it'll skip.
If you change
int str;
to
char str;
Your loop works as you seem to intend (tested in Visual Studio 2010).
Although, you should also probably check for str == 'n', since they told you that they were done.
...and only calculating the sum with my first initial input for i...
This is an expected behavior, because you are just reading the str and not using it. If you enter i >= 15 then loop must break, otherwise continues.
I think you wanted this thing
In this case total sum c will be less than 15 and continue to sum if user inputs y.
#include<iostream>
using namespace std;
int main()
{
int c=0;
int i=0;
char str;
do
{
cout << "Enter a num: \n";
cin >> i;
c = c + i;
cout << "Do you wan't to enter another num? y/n: \n";
cin >> str;
} while (c < 15 && str=='y');
cout << "The sum of the numbers are: " << c << endl;
return 0;
}

Input an integer, get spaced output in C++?

I'm working on homework and I'm stumped on this problem: Write a program that prompts the user to input an integer and then outputs both the individual digits of the number and the sum of the digits. For example, it should output the individual digits of 3456 as 3 4 5 6, [...], output 4000 as
4 0 0 0, and the individual digits of -2345 as 2 3 4 5.
Here's my code so far:
int main()
{
string a; //declares string
cout << "Type an integer: "; //prompts user to input an integer
cin >> a; //stores into string a
cout << "There are " << a.size() << " digits in " << a << endl; //retrieves length of string a
cout << a.at(0);
cout << endl;
system ("pause"); //pauses the system so user can read the screen
return 0; //returns 0 if program works properly
}
Can anyone enlighten me on what I'm doing wrong/what my next step is?
So the steps are..
store the input
display them all one by one separated by spaces
figure out the sum and display that
.
#include<string>
#include<iostream>
using namespace std;
int main()
{
string a;
cout << "Type an integer: ";
// 1. store the input
cin >> a;
// 2. display them all one by one separated by spaces
for(int i=0;i<a.size();++i)
cout << a[i] << ' ';
cout << endl;
// 3. figure out the sum and display that
int total = 0;
for(int i=0;i<a.size();++i)
total += a[i] - '0';
cout << total << endl;
system("pause");
return 0;
}
The tricky part is getting the correct sum in step 3.
total += a[i] - '0';
Lets say for example that a[i] is the character '4'. The ASCII value of character '4' is the integer equivalent of 52, and the ASCII integer equivalent of '0' is 48. Therefore if we take '4' - '0', we will get the difference of 4, which is the integer representation we are looking for in this case.
Here is a simple ASCII chart with character values.
Hope this helps!
You probably want to input the number as a string. This will allow you to do digit by digit processing. Then the user will enter the number once instead of many times as digits.
You could try this piece of code:
int num = 0;
cin>>num;
//Make sure array is large enough to hold all digits
//For an int 10 digits it the max
int digits[10] = {0};
//This variable tracks the count of actual number of
//digits extracted from user input
int digitCount = 0;
while (num > 0)
{
digits[digitCount] = num % 10; //Extract digit at units place
num = num / 10; //Advance through the number
digitCount++;
}
for(int count= digitCount-1 ; count >= 0; count-- )
{
cout<<digits[count]<<" ";
}
Note that the printing loop runs backwards (i.e from digitCount to zero) because the digits are extracted and stored starting from the units place. For a number a like 12345 the digits array will contain 5 4 3 2 1.
Rhonda, I can understand your frustration, computers are like that... they do what you say, not what you mean :-) Hang in there.
You say your program should output each of the digits in the number, yet your program asks the user to enter each of the digits. That is confusing.
Also, you first assign a value to "num" here
cin >> num;
then you overwrite "num" in this line
cin >> num >> a;
I'm not sure what you mean to do here, but what you're telling the computer to do is to read an integer from the input and assign it to "num" and assign the rest to the line to string "a"... if the rest of the line just has a space, the space will be discarded... it acts as a separator. That is probably confusing you as well.
int main()
{
int runningTotal = 0;
std::string inputString;
std::cin >> inputString;
for ( std::string::iterator _it = inputString.begin();
_it != inputString.end(); ++_it )
{
// *_it now represents an individual char of the input string
char a = *_it; char* b = &a;
if ( a != '-' )
{
runningTotal += atoi( std::string( b ).c_str() );
std::cout << *_it << " ";
}
}
std::cout << std::endl << "Total of all digits: " << runningTotal << std::endl;
std::cin.get();
std::system( "pause" );
return 0;
}
I threw this together quickly for you. Hope it's of help.

Use cin.clear() or cin,ignore() for ONLY previous line input?

Is there a way to use cin.clear() or cin,ignore() for ONLY the previous line of input without clearing ALL previous input? For example in my code I prompt the user for input for each month, well if the input is less than 0 I would like the program to clear that negative input so that it does not get total into my calculation. Problem is it clears ALL previous input which still screws up the calculation. Thanks for any ideas in advance.
// prompt user for input, keep a total sum of data entered
for(int i = 0; i < 12; i++)
{
cout << "Enter total rainfall for " << year[i] << endl;
cin >> month[i];
total += month[i];
while(month[i] < 0)
{
cout << "Ony enter positive numeric values!" << endl;
cin.clear();
cin >> month[i];
}
}
You seem to be mixing up two distinct issues. ios_base::clear()
doesn't remove any input; it resets the error status of the stream.
istream::ignore( n, ch ), on the other hand, reads forward until n
characters have been extracted or a character ch is seen'
myInput.ignore( INT_MAX, '\n' ) should ignore everything up to (and
including) the next '\n'.
but your code has one thing that is very strange:
cin << month[i];
You can't output to std::cin.
You probably want something like this:
unsigned int month[12];
for(size_t i = 0; i < 12; i++)
{
cout << "Enter total rainfall for month " << i+1 << endl;
while (!(cin >> month[i]))
{
cout << "Invalid input, try again." << endl;
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
// you probably want to repeat ignore() stuff here
// so in case user inputs something like 10x, the "x" that was left
// in the stream gets discarded
}
Note the array of unsigned integers. This way input like "-5" is automatically considered invalid so you don't need the less than 0 check. Clearing the entire stream shuouldn't worry you - if the input operation succeeds, the relevant part is already stored in your array.

Stack around the variable ' ' was corrupted

void GameBoard::enterShips()
{
char location[1];
int ships = 0;
int count = 1;
while(ships < NUM_SHIPS)
{
cout << "Enter a location for Ship " << count << ": ";
cin >> location;
cout << endl;
Grid[location[0]][location[1]] = SHIP;
ships++;
count++;
}
}
Im writing a battleship game. I have the board layouts working and the computers randomly generated ships. Now I am working on this method to prompt the user to enter coordinates for the ships When I run the program, it allows me to enter 5 ships. When I enter the 6th ship, it gives me this error.
Stack around the variable location was corrupted.
Ive looked for answers online and have not found anything exclusive.
Any help would be appreciated.
location is an array of a single char.
There is no location[1].
You are prompting the memory address of location array to your user. You should ask location indices separately:
void GameBoard::enterShips()
{
int location[2];
int ships = 0;
int count = 1;
while(ships < NUM_SHIPS)
{
cout << "Enter a location for Ship " << count << ": ";
cin >> location[0];
cin >> location[1];
cout << endl;
Grid[location[0]][location[1]] = SHIP;
ships++;
count++;
}
}
Notice int location[2]; since an array of size 1 can only hold one element. I also changed the element type to int. Reading char's from the console will result in ASCII values, which are probably not what you want.
cin >> location;
location is an array of one char. This can't succeed because when you read from a stream into a char array, a null terminator has to be added (which takes one character). You will inevitably overrun the bounds of the array.
You can use a std::string, which will help you avoid any buffer overrun issues:
std::string location;
if (!(std::cin >> location)) {
// handle input error
}
Note also that you probably need to convert the string representations of the numbers into numeric values. You can easily do this by reading from the stream into two int objects instead:
int x_location, y_location;
if (!(std::cin >> x_location >> y_location)) {
// Handle input error
}
if (x_location >= X_DIMENSION || x_location < 0 ||
y_location >= Y_DIMENSION || y_location < 0) {
// Handle out-of-range error
}
// use x_location and y_location
You made the location variable only able to hold a single character. You access it expecting it to hold at least 2 characters. If you're using cin and expecting to read exactly two characters, a better method would be:
char locationX, locationY;
// ...
std::cin >> locationX >> locationY;
// ...
Grid[locationX][locationY] = SHIP;