I've been trying to print out _ <------ this character in a 2D array... But when I
tried compiling the code, it returned some garbage numbers. I think I'm doing something wrong... can anyone please help me out to solve this problem ?
void main (){
int A[9][9];
for (int i=0; i<9; i++){
for (int j=0; j<i; j++){
A[i][j]= '_';//I am doing this part wrong.
}
}
for (int r=0; r<9; r++) {
for (int c=0; c<9; c++)
cout << setw(3) << A[r][c];
cout << endl;
}
system("pause");
}
A is an int array. So cout would try to print an integer. Try cout << char(A[r][c]);
The std::cout::operator<< operator is overloaded for several data types in order to facilitate (automagically-)formatted output. If you feed it an int, then it will print a number. If you give it a char, it will try to print it as a character. So either declare your array as an array of char, or cast the array member when printing:
cout << static_cast<char>(array[i][j]) << endl;
1. Assign the ASCII value to integer array rather than '_'. It will work even without change; but i feel it looks cleaner.
A[i][j]= 95; // try this instead of '_'
While printing, cout can print any data type without casting, but since we are looking for character to be printed, try explicit conversion.
cout << setw(3) << char(A[r][c]);
Not sure about the compiler you are using, but its a better practice to initialize the array to avoid garbage value tampering with your output
Related
Up until now I've been studying C, and now i wanted to try C++. Started out with some easy tasks. But I can't seem to find the answer, why is there a number either 0 or 488834... printed out.
I've tried re-declaring variables, using
for(n-1; n>=0; n--){
cout << a[n] << endl;
}
int main(){
int var = 0;
int a[100],n;
cin >> n;
for(int i=0; i<n; i++){
cin >> a[i];
var++;
}
for(var-1; var>=0; var--){
cout << a[var] << endl;
}
Everything works, except that 0/some number in the middle of the output
Result
In the following line:
for(var-1; var>=0; var--){
var-1 doesn't actually modify the value of var. So var gets to keep its original value, which means the first value you end up printing is what is after the end of the original sequence.
Use var = var - 1 instead.
In your second for loop you don't have an assignment, just a statement. You start printing from a location of the array that contains an invalid number due to this, you may want too have your second loop read
for(var = var-1; var>=0; var--){
cout << a[var] << endl;
}
Now, there are more element ways to write this, but this is a fix that is needed in your code.
Trying to insert values into a 2D array, but the output isnt giving my values, instead random letters
int myArr[8][2] = {700,730,760,790,810,840,910,1000}{0.011,0.035,0.105,0.343,0.789,2.17,20,145};
cout << myArr << endl;
system("Pause");
How should I adjust the code, or is it easier to use a text file and insert?
Numerous problems:
the array dimensions are wrong
you don't have outer braces or a comma for the nested arrays
you're trying to store double precision floating point values in an int array
you can't use cout with an entire array.
The array declaration should probably be something like this:
double myArr[2][8] = { {700,730,760,790,810,840,910,1000},
{0.011,0.035,0.105,0.343,0.789,2.17,20,145} };
and to output the contents you could do something like this:
for (int i = 0; i < 2; ++i)
{
for (int j = 0; j < 8; ++j)
{
cout << " " << myArr[i][j];
}
cout << endl;
}
Live Demo
First - you can't print the whole array just by using cout << myArr, you need to iterate over the elements of the array using a for loop.
Second - you are trying to put decimal values into an integer array which will truncate all of the decimals.
Third - Your array should be sized myArr[8][2] not myArr[2][8]. I'm surprised your compiler lets you get away with this. You should probably look into using a different compiler.
You need to iterate through each row and column, otherwise you're just printing out the pointer value of the array handle.
for (int i=0;i<8;i++){
for (int j=0;j<2;j++){
cout << myArr[i][j] << " ";
}
cout << endl;
}
system("Pause");
I am basically trying to store everything after a certain index in the array.
For example, I want to store a name which is declared as char name[10]. If the user inputs in say 15 characters, it will ignore the first five characters and store the rest in the char array, however, my program crashes.
This is my code
char name[10];
cout<< "Starting position:" << endl;
cin >> startPos;
for(int i= startPos; i< startPos+10; i++)
{
cout << i << endl; // THIS WORKS
cout << i-startPos << endl; // THIS WORKS
name[i-startPos] = name[i]; // THIS CRASHES
}
For example, if my name was McStevesonse, I want the program to just store everything from the 3rd position, so the end result is Stevesonse
I would really appreciate it if someone could help me fix this crash.
Thanks
Suppose i is equal to 3. In the last iteration of the loop, i is now equal to 12, so substituting 12 in for i, your last line reads
name[12-startPos] = name[12];
name[12] is out of bounds of the array. Based on what you have shown so far, there is nothing but garbage stored in name anyway before you start doing this assignment, so all you're doing is reorganizing garbage in the array.
Please in future: post full compilable example.
A simple answer is that your array maybe is out of bound, since you don't provide full example its hard to know exactly.
Here is a working example:
#include <iostream>
using namespace std;
int main() {
int new_length, startPos;
int length = 15;
char name[15]= "McStevesonse";
cout<< "Starting position:" << endl;
cin >> startPos;
if(new_length <1){ // you need to check for negative or zero value!!!
cout << "max starting point is " <<length-1 << endl;
return -1;
}
new_length=length-startPos;
char newname[new_length];
for(int i= 0; i<new_length; i++){
newname[i] = name[i+startPos]; // THIS CRASHES
}
cout << "old name: " << name << " new name: " << newname << endl;
return 0 ;
}
To put it simply, change this:
for(int i= startPos; i< startPos+10; i++)
To this:
for(int i= startPos; i<10; i++)
You should be fine with that.
Explanation:
At some point, when you use the your old loop, this name[i-startPos] = name[i] would eventually reach an array index out of bounds and causes the crash.
Don't forget to clean up/hide the garbage:
Doing so, would cause the output to produce some kind of garbage outputs. If you got a character array of 'ABCDEFGHIJ', and have chosen 3 as the starting position, the array would be arranged to 'DEFGHIJHIJ'. In your output, you should atleast hide the excess characters, or remove by placing \0's
So, I'm getting the above error (in the title) but for some reason it's only throwing this error on the second loop. Notice the first and second loop I have using the customer variable works absolutely fine, no errors thrown or anything. But on that last loop, the output[customer][charge] array, there is a red line under output[customer] that says "Subscripted value is not an array, pointer or vector". I am using xcode, Mavericks OSX. All of my arrays are defined elsewhere, and have worked perfectly the whole length of the program until now. There are some other operations going on in the program, but they have nothing to do with this loop, so I just posted the code that was giving the error. Again I'll say, the charges[customer][month][charge] loop works fine, but the output[customer][output] is not working.
P.S. You probably will think the logic behind keeping all this data in numerically indexed arrays is dumb, but it is for a school project. So don't lecture me about how this program is logically inconsistent or whatever. Thanks!
string headings[3][7];
string chargeLabels[3] = {"Electricity :","Water: ","Gas: "};
string outputLabels[5] = {"Subtotal: ","Discount: ","Subtotal: ","Tax: ","Total: "};
double charges[3][3][3];
double output[3][5];
for(int customer=0; customer<3; customer++)
{
for(int heading=0; heading<5; heading++)
{
cout << headings[customer][heading];
}
for(int month=0; month<3; month++)
{
cout << chargeLabels[month];
for(int charge=0; charge<3; charge++)
{
cout << charges[customer][month][charge] << ", ";
}
cout << endl;
}
for(int output=0; output<5; output++)
{
cout << outputLabels[output];
//error is below this comment
cout << output[customer][output] << endl;
}
}
Inside the for statement:
for(int output=0; output<5; output++)
{
You declared another variable int output which shadows the double output[3][5] with the same name outside the for statement.
Here's your problem:
double output[3][5];
for(int output=0; output<5; output++)
You're reusing output as a variable name twice.
So when you try to access it here:
cout << output[customer][output] << endl;
You're accessing the local output, which is just an int.
First off, this is a "homework" question so vector libraries and string libraries are off limits. I'm trying to get to the basics of c++.
My intention with this code is to make and use an array of string arrays. A list of words in other words.
When I run this code I get a bunch of nonsense.
If there is a better way to make a list of words in c++, I would love to hear about it.
const int cart_length = 50;
const int word_length = 50;
int main()
{
char cart_of_names[cart_length][word_length];
float cart_of_costs[cart_length];
char name[word_length];
cout << "enter the name of the first item: ";
cin >> name;
for(int i=0; i<word_length; i++)
{
cart_of_names[0][i] = name[i];
}
cout << endl;
cout << "that is: ";
for(int x=0; x<word_length; x++)
{
cout << cart_of_names[0][x];
}
cout << endl;
return 0;
}
If the string entered is not 50 characters long (cart_length), then less than 50 characters will be valid in the name. You should have an if(cart_of_names[0][x]==0) break; in your second loop.
I don't exactly understand what you are looking for. Following code will help you to read and print a list of 50 words. Hope this would help you.
const int cart_length = 50;
const int word_length = 50;
int main()
{
char cart_of_names[cart_length][word_length];
float cart_of_costs[cart_length];
for(int i=0; i<cart_length; i++)
{
cout << "enter the name of the " << i + 1 << "th item: ";
cin >> cart_of_names[i];
}
cout << "that is: ";
for(int x=0; x < cart_length; x++)
{
cout << cart_of_names[x] << endl;
}
return 0;
}
Check out STLSoft's fixed_array_2d (and it's higher order siblings). There's a detailed discussion of how they're implemented for maximum performance in Matthew Wilson's Imperfect C++.
If you can't use std::string, at least look at the functions like strncpy() from C for your name copying. Also, you're forgetting that c-style strings are null terminated.
Unless you're forbidden to use STL (which would be just mean), just use std::list<std::string>. www.cplusplus.com has detailed descriptions and examples for those classes.
Otherwise, you're stuck with an array of char arrays: in that case, be prepared for a lot of buffer overflow errors. Look around on the above site for the char[] management functions (strncpy() and the like), they'll make your life a bit easier (but not a lot).
In C, the best way I found to conceptualize what you are trying to do is using an array of char*. Same effect, but if you start to work with it I believe you may find it is easier on the brain.
It looks pretty close to me. Strings in C are null-terminated, which means that the end of the string is indicated by a null character. In a sense, a string in C is really just an array of bytes.
When you do:
cout << "enter the name of the first item: ";
cin >> name;
If I enter the string "Book", in memory it'll look like something like:
|0|1|2|3|4|5..49|
|B|o|o|k|0|*HERE BE DRAGONS*
Well, really it will contain the ASCII values corresponding to those letters, but for our purposes, it contains those letters. There here be dragons is memory that that you didn't initialize, so it contains whatever garbage your platform sets it to.
So when you copy your string, you need to instead look for that 0 byte at the end of the string.
for(int i=0; name[i]!=0; i++)
{
cart_of_names[0][i] = name[i];
}
Then when you output it, you don't actually need to do it a character at a time. You can just do cout<<cart_of_names[0]. cout knows where the string ends because of that terminating null character.
If you use strcpy() instead of
cart_of_names[0][i] = name[i];
it may work better but I cringe just looking at all that code.
"If there is a better way to make a list of words in c++, I would love to hear about it."
Include #include <string> and use std::string. The std::string type is part of the C++ specification, I think.
#include <iostream>
#include <string>
int main(void) {
std::string list[7];
list[0] = "In C++";
list[1] = "you can use";
list[2] = "the `std::string` type.";
list[3] = "It removes";
list[4] = "many of the problems";
list[5] = "introduced by";
list[6] = "C-style strings.";
for (int k=0; k<7; k++) std::cout << list[k] << ' ';
std::cout << '\n';
return 0;
}