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Hi guys
I am trying to write a program that uses a loop to display the characters for ASCII codes 0 through 127. But the catch is 16 characters are to be displayed on each line.
I have tried working on this program numerous time but haven't gone anywhere yet. any suggestions
Sure, make a normal loop and check for modulus loop variable 16 is equal to 0, and if so, print a newline.
In the loop, just print the ASCII character.
Hay thanks for ur help. But can you add more details since i am still a noob in C++ .
Do i have to use 2 loops.. one loop inside the other ?
Sample code:
Code:for (int i = 0; i <= 127; i++)
{
if (i % 16 == 0) // This is true only once every 16 loops, when i is dividable by 16 with no rest (ie a whole number, not 2.7897535...)
{
// Print a newline
}
// Print your character
}
ok here what i wrote
and i am getting the following error messageCode:int main()
{
char a =0;
int i;
for (int i = 0; i <= 127; i++)
{
if (i % 16 == 0)
{
cout<<endl;
i=a;
}
cout<<a;
}
return 0;
}
Quote:
multiple declartion of i in the fuction main.
See comments. The error is because you have two i variables. Remove one.Quote:
Originally Posted by wolverine12345
lol i feel like an idiot now..
ok i removed the int i; and getting no errors but when i run the program, it hangs.. one of those infinite loops..
and the reason i am using i=a so a has the same value as i . a is a character variable. so whenever i changes a changes and displays the character
Erm, you're doing it the wrong way then. You're assigning a to i. Besides, you don't need a. Just print out i.
So simple, yet so powerful.Code:cout << static_cast<char>(i);
And the reason for the infinite loop is because you're assigning a to i (since a is always 0... well, you get my point).
[edit] @Elysia: consider recommending C++-style casting (static_cast<>()) rather than C-style casting (()) in this forum, the C++ one. [/edit]
Well then you should have it outside the if statement, and it should be a=i, not i=a. You're just setting i to some randome value (because a isn't initialized) with your statement.Quote:
and the reason i am using i=a so a has the same value as i . a is a character variable. so whenever i changes a changes and displays the character
By the way, you can get away with a cast instead of your variable a:
That causes i to be treated as a character, and cout will print a space instead of 32 or whatever.Code:cout << static_cast<char>(i);
It should be noted that you can use the isprint() function from <cctype> to determine whether a character is a normal character that can be printed. You see, many of the characters from 0 to 32 and from 127 to 255 are unprintable, or mess up your screen if you do print them. Backspace, delete, beep, newline, formfeed, carriage return, tab, and more are characters in these ranges that will mess up your display. Consider using isprint().
You must be using MSVC 6. It's the only compiler that I know of that would complain with this code:
That's valid C++, by the way -- although redundant, because the outer i is never used.Code:int i;
for(int i = 0; i < 10; i ++) {}
Thank you Elysia and dwks
The program is running fine now
I really appreciate your help.
just one quick last question.
Is there any quick way to find out the highest and lowest number from a list of numbers. The method that i can think of at the moment is using the if statements . e.g
if we have 6 numbers a,b,c,d,e,f then
if a>b>c>d>e>f cout<< a is highest
if b>a>c>d>e>f cout<< b is highest
if c>a>b>d>e>f c out << c is highest
and so on
but it will take forever to write if we have let's say 1000 numbers..
any suggestions ?
I forgot :p I'm used to C-style casting. Bad habit I'm trying to get rid of, but I usually don't do any bad casting so I haven't really run into troubles using C-style casting, pretty much explaining why I haven't used much C++-style casting.Quote:
Originally Posted by dwks
Believe there are CRT functions for that? Don't know for sure, but I do know there was a thread about it somewhere. Someone else might just help you out there, as well, though, because I don't really know.Quote:
Originally Posted by wolverine12345
It's not too difficult if you use arrays. If you use a separate, named variable, then you have to use something like this.
Ouch.Code:max = MAX(a, MAX(b, MAX(c, d) ) );
Consider using arrays. Then it's quite simple. You can use a loop to loop through every element, comparing that element with the maximum value found so far. If this element is larger than the previously known maximum, then you set the maximum to this element.
Do you know how to use arrays? http://www.cprogramming.com/tutorial/lesson8.html
ok here what i wrote
Code:int main()
{
const int number = 10;
int num[number];
int max=0;
int min;
cout<<"Please enter 10 numbers."<<endl;
cin>>num[0];
cin>>num[1];
cin>>num[2];
cin>>num[3];
cin>>num[4];
cin>>num[5];
cin>>num[6];
cin>>num[7];
cin>>num[8];
cin>>num[9];
for (int i= 0; i < 10; i++)
if (num[i] > max)
max = num[i];
cout << "The highest number is " << max<< endl;
for (int j= 0; j < 10; j++)
if (num[i] < min)
min = num[i];
cout << "The lowest number is " << min<< endl;
return 0;
}
The program seems to find the highest number but for the lowest number it would give me a random value. e.g whenever i enter 1,2,3,4,5,6,7,89,10 . highest number is 10 but for the lowest number it would give me value like 8890.. etc
'Nuff said ;)Quote:
Originally Posted by wolverine12345
Btw, that shouldn't even work but due to a compiler bug, quirk or whatever, vars declared inside a for becomes global for the function or block in MSVC6, which goes against the standard.
In case Elysia wasn't being clear: you're using i instead of j.
Be sure to initialize min as well. And setting max to 0 would backfire if all the numbers were negative. Either set it to INT_MIN (from <climits>) or num[0], once you read in the numbers. (Setting it to num[0] is easier, but doesn't work if there are no elements in the array.)
Consider using a loop, it would be much simpler.Code:cin>>num[0];
cin>>num[1];
cin>>num[2];
cin>>num[3];
cin>>num[4];
cin>>num[5];
cin>>num[6];
cin>>num[7];
cin>>num[8];
cin>>num[9];
Ah yes, loops. Didn't think of that >_<
Always initalize variables, so initialize min and max to 0x80000000 (or just INT_MIN) (max negative value for ints). That should take care of some problems.
Elysia, you don't want to initialize "min" to the smallest possible number, right?
I quite like dwks suggestion of using the first element in the array - it's an easy option [and you get one less compare - which will improve the performance in this case by 10% - that must be the clincher, right? :) ]
--
Mats
It's a bad idea to use constant values for INT_MIN. Of course, if you must insist, this gives you an approximate negative value:Quote:
Originally Posted by Elysia
Leave off the -1 and you get the absolute minimum for ints on two's complement machines (which are the most common), but break it on other machine types.Code:-((unsigned)-1 / 2 - 1)
Or something that would work for one- and two's complement machines:
Or just be standard and portable and simple and use INT_MIN!Code:#define MIN(x) ((x) < (y) ? (x) : (y))
#ifndef INT_MIN
#define INT_MIN MIN((int)-((unsigned)-1 / 2), (int)-((unsigned)-1 / 2 - 1))
#endif
Code:#include <climits>
/* ... */
int min = INT_MIN;
Well, now that I think of it, maybe not. Perhaps the biggest number, INT_MAX would be better. And INT_MIN for the lowest, of course.Quote:
Originally Posted by matsp
If you are finding the min value after finding the max value of the numbers entered by the user, just set min = max, after the max loop and before the min loop. then you will have both without a lot of fuss.
D'oh . . . *brain freeze*
In other words, you want
Confusing, no?Code:int max = INT_MIN, min = INT_MAX;
Yes, indeed, initializing both elements to num[0] is a much better idea, assuming that you know that num[0] has a value. And of course, if you do this, the loop can start at 1 instead of 0, saving an iteration, as matsp has obsevered.
[edit] clegs' idea would work, but it depends on at least one element being in the num[] array as well. So using INT_[MIN|MAX] would work as well -- and might be more efficient because those values are constants. Plus you could save that one loop iteration with this method as well! :) [/edit]
But you may just as well use the first element of the array - as that saves one compare, and is more likely to be the min value - the max value is definitely NOT the min value [unless all values are equal, in which case the first value will also be the smallest and largest].Quote:
Originally Posted by clegs
--
Mats
No, not at all! Looks perfectly fine and dandy!Quote:
Originally Posted by dwks
Btw, since we don't know which element of the array will hold the maximum or minimum value of all the entered ones, I believe it's quite a risk to do much else than using those constants to initalize max/min.
No this is what I mean:
for (int i= 0; i < 10; i++)
if (num[i] > max)
max = num[i];
cout << "The highest number is " << max<< endl;
min = max;
for (int j= 0; j < 10; j++)
if (num[i] < min)
min = num[i];
cout << "The lowest number is " << min<< endl;
If finding the max works then use it as the highest number, print it out, then set the max value to min and start the min loop. You will find the min of all numbers entered by the user.
Yes it works - but if the array is EMPTY, the min/max value is surely "undefined" - an empty array can not have a min or max value, right? It's a bit like "divide by zero": "every possible answer is the right and wrong answer at the same time". [You could of course DEFINE that IN CASE OF EMPTY ARRAY, the max/min values are DEFINED to be [10000, -10000] or [0,0] or [INT_MIN, INT_MAX] or whatever - but an empty array contains nothing, so it can't have a min or max value].Quote:
Originally Posted by dwks
--
Mats
Sure, it works But if we do:Quote:
Originally Posted by clegs
We save a couple of comparisons (no need to compare num[0], and almost CERTAINLY change it), and end up with exactly the same result. By doing both compares in the same loop, we save some more computation too - there's no point in searching for the max separately from min - we still need to compare all [but the first] elements.Code:min = max = num[0];
for (int i= 1; i < 10; i++) {
if (num[i] > max)
max = num[i];
if (num[i] < min)
min = num[i];
}
cout << "The highest number is " << max<< endl;
cout << "The lowest number is " << min<< endl;
Of course, saving one iteration of a loop of 10 is 10%, but if the loop is 10000, it's somewhat less of a saving... [0.01%]. Doing one loop instead of 2 is a good saving in both cases. For large loops, on a compiler that allows it, you may also want to consider saying "unlikely" to the if-statement, because unless you have a set of numbers that are continually rising or falling, likelyhood is that you pretty soon have a number that is at least close to max or min, and rarely go into the "true" side of the if.
--
Mats
But of course. If you can deal with empty arrays, then it's much easier to do so before you go calculating the minimum or maximum or average or whatever of the elements in the array.Quote:
Yes it works - but if the array is EMPTY, the min/max value is surely "undefined" - an empty array can not have a min or max value, right? It's a bit like "divide by zero": "every possible answer is the right and wrong answer at the same time". [You could of course DEFINE that IN CASE OF EMPTY ARRAY, the max/min values are DEFINED to be [10000, -10000] or [0,0] or [INT_MIN, INT_MAX] or whatever - but an empty array contains nothing, so it can't have a min or max value].
On the other hand, if you must have a value, for example withCode:if(elements == 0) { /* empty */ }
else { /* calculate min/max/avg/whatever */ }
then you might have to return INT_MIN to deal with an empty array.Code:int array_min(int array[], size_t elements)
There's yet another disadvantage of using INT_MIN and/or INT_MAX. If all of the elements in the array are INT_MIN, for example, then the calling function couldn't tell the difference between this situation and the case of zero elements.
All told, it's best to use min = num[0]. :) No issues about an empty set of numbers actually having a minimum, no possible problems with very high or very low numbers, and greater efficiency!
So why would the program get to the point of finding the min value if the array was empty, wouldn't that be a discovery in finding the max (or before with an assert statement)? I was just adding a possible solution of finding a starting point for finding min, use the max value in the array which was found in the previous loop.
I am just a student, and that is my simplistic view. Sorry!
You're right, it's a viable solution. It's just that using INT_whatever is possibly more efficient, and works as well. And min = num[0] is more efficient still, assuming the array isn't empty.
We're not blaming you for anything. Your suggest was not a bad one, though if you initialize max/min, it probaly wouldn't be necessary.Quote:
Originally Posted by clegs
matsp's suggestion was the best one. We were all outsmarted :p
Ahem, I suggested it first! :D
Actually it's a well-known solution, so neither of us deserves praise . . . .
Ah, it got lost somewhere in the thread! I see it now.
You outsmarted as all :p Actually, I didn't know there was such an optimization. Well, I don't really work with loops that way. Often... anyway... I think...
lmao.. found my stupid mistake..
thanks guys..
one more quick questions guys
how can i make a program reject a negative value from being stored in array. e.g if a user inputs a negative value, how can i display a message that will tell the user to enter a positive value.
Guess. Maybe something along the lines of
- Get a number from the user.
- If the number is negative:
- Print an error message.
- Get another number from the user.
- Go to step 2.
- Viola! You have your number.
That can be simplified, of course, for example if you use a do-while loop instead . . . but try that and see what happens.