how viable would it be if we had a sticky on a pointers tutorial? Or a quick refresher - i always end up linking to wikipedia then a couple of college sites when explaining pointers over the net on forums (mostly code comments, cramster etc).
it'd be awesome if we can get a collaborative effort on making the best pointers tutorial on the net ...
Help with assignment 4
Im trying to input a number with at least three digits:
heres what i did
#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
int number;
count << "Enter a number:";
cin >> number;
cin.ignore();
if (number == setprecision(3) )
{
count << "Number has 3 digits." << endl;
}
else
{
count << "It is not a 3 digit number." << endl;
}
cin.get();
return 0;
somethings wrong and i know its the number == setprecision(3) what should i do?
by the way i just finished number 2 in assignment 4
please check and is there any other shortcut method ?
#include <iostream>
using namespace std;
int main()
{
char character;
count << "Enter any letter from A to Q: ";
cin>>character;
cin.ignore();
switch (character) {
case 'A':
case 'B':
case 'C':
case 'D':
case 'E':
case 'F':
case 'G':
case 'H':
case 'I':
case 'J':
case 'K':
case 'L':
case 'M':
case 'N':
case 'O':
case 'P':
case 'Q':
count << character;
break;
default:
count << "Letter not in the list. " << endl;
I briefly looked over the C++ tutorial, and it looked fairly good. One thing though - maybe you should mention the Code::Blocks IDE (http://www.codeblocks.org), and that if one decides to use it, they should use the latest Nightly Build. Although Dev-C++ is still pretty good, it is getting old, and Code::Blocks is becoming better and better than it.
#include <iostream>
#include <conio.h>
#include <iomanip>
#include <cmath>
using namespace std;
main()
{
long double num1, num2, num3;
int number, num4, reset = 1;
do {
cout << "1. Hypotenuse" << endl << "2. Other" << endl;
cin >> number;
switch (number) {
case 1:
cout << "Enter the two sides, each followed by the enter key" << endl;
cin >> num1 >> num2;
num2 = sqrt(num1*num1 + num2*num2);
break;
case 2:
cout << "Please enter the hypotenuse" << endl;
cin >> num1;
cout << "Please enter the other side" << endl;
cin >> num2;
num3 = sqrt(num2*num2 - num1*num1);
cout << num3 << endl;
break;
}
num3 *= 1000;
num1 = num3 - floor(num3);
num1 *= 10;
num1 = floor(num1);
if (num1 >= 5) {
num3 = ceil(num3);
} else {
num3 = floor(num3);
}
num3 /= 1000;
cout << "Thankyou, the desired length is: " << num3 << " to 3d.p." << endl;
cout << "Would you like to reset? (1 to reset)" << endl;
cin >> reset;
} while ( reset == 1);
return 0;
}
edit:
i have improved it, with menu system and other side calculation but I am having trouble getting a big enough variable to hold a number bigger than 9 as well as with 3 or more decimal places... it seems long double isn't enough...
what should i be using?
still have no idea about the 3 digit assignment...
and for pascal, i created my own functions and then fiddled to troubleshoot. i had the program automatically enter row 0 and then i set the first position of each row to 0...
but still i don't even know where to start on the 3 digit one...
1. Yes, C is different from C++. C is pretty much (but not completely) a subset of C++. C++ is basically C with object-oriented features.
2. You don't really download C/C++. You can download a C/C++ compiler, linker, and editor, or an IDE (integrated development environment - pretty much combines the compiling, linking, and editing processes) . If you're using windows, you might want to try Dev-C++ or Code::Blocks (if you choose to use Code::Blocks, I recommend getting the latest Nightly build - read the stickied threads at the link for more information on using Nightly builds). Dev-C++ and Code::Blocks are both IDEs, by the way.
First off, dduardo, thank you for what has been, so far, a most excellent tutorial.
Having said that, the pascals triangle task has seemed daunting to me, and I had to look up how to make my own functions to do it efficiently, and I came up with this:
Code:
#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
long double factorial (int num)
{
if (num==1)
return 1;
return factorial(num-1)*num; // recursive call
}
int pscl (int n, int r)
{
int out;
long double nf=factorial(n), rf=factorial(r), nrf=factorial(n-r);
long double btm=rf * nrf;
long double tout=nf/btm;
out = (int)tout;
return out;
}
int main(int argc, char *argv[])
{
int rin;
int nin;
int pout;
cout << "input row: ";
cin >> rin;
cout << "input number: ";
cin >> nin;
pout=pscl(nin, rin);
cout << pout << endl;
system("PAUSE");
return EXIT_SUCCESS;
}
the function 'factorial' is fairly obvious, and is a double float because factorials can be big. 'pascal' uses the binomial coefficient thing to calculate the number at a given place and row (n, r).
but this code crashes, and the debugger (when it decides to work) tells me it gets an 'access violation'. I tried breakpoints, but as I said, the debugger is a bit temperamental. Can you see anything wrong with my code?
No idea what the original question were, but I can tell you your program is crashing because / when the end user is entering a number for 'rin' that's larger than 'nin'. I.e. when 'n-r' < 0. (It might also crash when n-r == 0, but too lazy to try.)
Could you be kind enough to explain why it's crashing when n-r==0 ?
EDIT: I changed the condition for the if statement in 'factorial' to (num==1 || num==0) and now it works fine. I'm never nicking code off the internet again.
Thanks for bringing it to my attention. I can't believe I didn't spot that after going over the problem for 40 minutes.
Hey Guys can you help me w/ my algorithm for sin(x), the correct value won't appear
#include <cstdlib>
#include <iostream>
#include <iomanip>
using namespace std;
int main(int argc, char *argv[])
{
int x,j;
double N,T,S,D,X;
count<<"Enter Value of x:"<<endl;
cin>>x;
count<<"Enter No. of Iterations:"<<endl;
cin>>j;
count<<endl;
X=(x*3.1416)/180; //conversion from degrees to rad
N=X; //inital value
D=1; //inital value
T=1; //inital value
S=1; //inital value
count<<"i"<<"\t\t"<<setw(6)<<"Term"<<"\t\t"<<"cos("<<x<<")"<<endl;
count<<endl;
for(int i=1;i<=j;i++)
{
N=(-N)*X*X;
D=D*(2*i)*((2*i)+1);
T=N/D; //term
S=S+T; //summation
count.setf(ios::fixed|ios::showpoint|ios::left);
count<<i<<setprecision(3)<<"\t\t"<<T<<"\t\t"<<setprecision(5)<<S<<endl;
}
count<<endl;
count<<endl;
count<<"sin("<<x<<")"<<"="<<S<<endl;
system("PAUSE");
return EXIT_SUCCESS;
}
i derived the formula from the expansion of the function of sin(x) which is
x-(x^3/3!)+(x^5/5!)-(x^7/7!)... pls help me..whats wrong w/ my program =(..it won't seem to display the cortrect value..
First off, dduardo, thank you for what has been, so far, a most excellent tutorial.
Having said that, the pascals triangle task has seemed daunting to me, and I had to look up how to make my own functions to do it efficiently, and I came up with this:
Code:
#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
long double factorial (int num)
{
if (num==1)
return 1;
return factorial(num-1)*num; // recursive call
}
int pscl (int n, int r)
{
int out;
long double nf=factorial(n), rf=factorial(r), nrf=factorial(n-r);
long double btm=rf * nrf;
long double tout=nf/btm;
out = (int)tout;
return out;
}
int main(int argc, char *argv[])
{
int rin;
int nin;
int pout;
cout << "input row: ";
cin >> rin;
cout << "input number: ";
cin >> nin;
pout=pscl(nin, rin);
cout << pout << endl;
system("PAUSE");
return EXIT_SUCCESS;
}
the function 'factorial' is fairly obvious, and is a double float because factorials can be big. 'pascal' uses the binomial coefficient thing to calculate the number at a given place and row (n, r).
but this code crashes, and the debugger (when it decides to work) tells me it gets an 'access violation'. I tried breakpoints, but as I said, the debugger is a bit temperamental. Can you see anything wrong with my code?
Ack! There are FAR more efficient ways to calculate Pascal's triangle than to use a factorial function. I think the Mathworld page failed to explain the key property of Pascal's Triangle, which was Pascal's original motivation in the first place:
The numbers in each row are obtained by adding the two numbers above them in the previous row.
Maybe you should try re-writing your program not using any factorial function. Even a long double will not be big enough for you to get a triangle more than 20 rows or so. And it will also be inaccurate due to rounding errors (a double only holds 15 significant digits of accuracy; it represents higher numbers by using scientific notation).
If you use a more efficient method (simply summing terms from the previous row), then you can create huge triangles using only ints, and your program will run much, much faster.
Assignment 3 requires use of the sqrt() function and the math.h library. The tutorial before that point doesn't mention them. Not sure whether or not you meant to leave them for the reader to find out on his own, but if not it might make sense to add them.
Well, It can be wrong but I think C would be better, since it is an event driven programming language and it work faster, in more efficient way.
C is procedural, not event driven.
Can anyone please try to see what's wrong with this program? I wrote it for school, to help simply radicals. It seems to work fine most of the times. However there is a problem when trying to simply perfect cubes. Try and entering 64 with an index of 3, it'll give you an unexpected answer. Now try entering 8 with an index of 3, and it'll give you the right answer. I have tried debugging it, but it's not making any sense to me. I am sorry if this shouldn't be posted here, let me know and I can move it. :)
Code:
#include <iostream>
#include <math.h>
typedef struct
{
double x, y;
}pair;
bool breakcube(double radi, double inx, pair& pr)
{
double cb = 0;
for (int i = 2; i < radi; i++)
{
cb=i;
for (int j = 1; j < inx; j++)
cb*=i;
for (int j = 1; j < radi; j++)
{
if (cb*j==radi)
{
pr.x = cb;
pr.y = j;
return true;
}
}
}
return false;
}
int main()
{
double radi = 0;
double cb = 0;
double inx = 0;
char buff[500];
while(true)
{
std::cout << "\nEnter radicand ('quit' to terminate): ";
std::cin >> buff;
if (!strcmp(buff, "quit"))
return 0;
radi=atof(buff);
std::cout << "\nEnter index: ";
std::cin >> inx;
cb = pow(radi, 1.0/inx);
if (cb == (int)cb)
{
std::cout << "\nPerfect " << inx << " : ";
for (int i = 0; i < inx; i++)
{
std::cout << cb;
if (i!=inx-1)
std::cout << " * ";
}
std::cout << " = " << pow(cb, inx);
continue;
}
pair pr;
if (breakcube(radi, inx, pr))
std::cout << "\n" << radi << " can be broken by: " << pr.x << " * " << pr.y;
else
std::cout << "\n" << radi << " cannot be broken";
}
return 0;
}
guys can somebody help me with a java programming? It's a really short homework but I'm just stucked there. Here is the code if u can please teplay to me asap.
public class DaysPerWeek
{
public static void main(String[] args)
{
final int DAYS_PER_WEEK = 7;
int days;
int weeks;
int totalDays;
Scanner scan = new Scanner(System.in);
System.out.println("This program convert days to week");
System.out.print("Enter number of days; ");
days = scan.nextInt();
days = totlaDays % DAYS_PER_WEEK;
weeks = totalDays / DAYS_PER_WEEK;
System.out.println("Days Per Week" + totaldays);
}