When running my program through cs50's submit50 check, everything works besides validating 4222222222222 as VISA (instead of INVALID) is output. When I print out the count variable before, then sometimes VISA is output. Any solutions would be much appreciated as I cannot seem to properly fix this.
INSTRUCTIONS: Write a program that prompts the user for a credit card number and then reports (via printf) whether it is a valid American Express, MasterCard, or Visa card number, per the definitions of each’s format herein. So that we can automate some tests of your code, we ask that your program’s last line of output be AMEX\n or MASTERCARD\n or VISA\n or INVALID\n, nothing more, nothing less
#include <stdio.h>
#include <cs50.h>
int main(void)
{
//get input from user
long CardNum = get_long("Input credit card number:");
bool nvalid = true;
//count number of digits
int count = 0;
long temp1num = CardNum;
while (temp1num > 0)
{
temp1num = temp1num / 10;
count++;
}
//printf("%i\n", count);
if (!(count == 13 || count == 15 || count == 16))
{
printf("INVALID\n");
}
else
{
.....
The problem arises in the beginning of the code so I only copied that part.
Mastercards always starts with either 5 or 2 and has a length of 16.
Visa cards always start with a 4 and can have a length of 13-16-19.
You are close. Try adding an additional condition for the supported lengths for VISA in your if statement it should solve your problem. Or, why not just check if the card length is either 13 - 19? It seems like it's failing because Visa supports different card lengths.
I have an awesome helper method that determines card types that's extremely handy but it's in C#.
Related
(I'll start by noting this lab is low level 1st year programing, so high level stuff isn't usable right now for us)
I was given a lab to write a program in C that would accept a number between 1 and 36, six times, then print out those numbers as a bar graph, where the 'bar graph' is a number of # equal to the input number.
e.g. 5 would be:
So far I have this:
#include <stdio.h>
void graphCreate();
int main(void)
{
graphCreate();
}
void graphCreate()
{
static int chartLoop = 1;
int graphLength = 0;
int graphNumber = chartLoop;
while(graphLength > 36 || graphLength < 1)
{
printf("How long is chart %d?\t", graphNumber);
scanf("%d", &graphLength);
}
if(chartLoop < 6)
{
chartLoop++;
graphCreate();
}
printf("\n%d.\t%d|", graphNumber, graphLength);
while(graphLength > 0)
{
printf("#");
graphLength--;
}
}
And it does the output as expected... mostly:
How long is chart 1? 5
How long is chart 2? 10
How long is chart 3? 15
How long is chart 4? 20
How long is chart 5? 25
How long is chart 6? 30
6. 30|##############################
5. 25|#########################
4. 20|####################
3. 15|###############
2. 10|##########
1. 5|#####
However, I need the final outputs (the bars) in 1 -> 6 order, and it's reversed. What am I doing wrong that it's in reverse?
If using the recursive way to solve the problem is a requirement, you need to store the outputs and then print them in reverse order.
If recursive is not a requirement, you can loop 6 times to get and store the input numbers and print the bars in sequence.
I want to code a simple bean machine program. The program will accept user input for the number of balls and the number of slots, and will calculate the path of each ball. The number of balls in each slot will be printed as a histogram as well.
I tried my best to keep the code short and sweet, yet the best I have managed is 112 lines long. When I ran my code, I received no errors. However, the output seems to have run into some sort of an infinity loop (The '#' symbol which was used to represent numbers in the histogram keeps on printing forever for some reason unknown to me).
Apparently, there is something wrong with my logic somewhere... or a silly little mistake in syntax(but it would have shown up as error, wouldn't it?)... In a nutshell, I cannot figure out exactly what is the problem. (I attempted to walk through the whole code process from start to finish, but my mind kept getting tangled up somewhere in the middle of the code, nowhere near the end of the code either).
Where exactly does my logic go wrong?(Or have I taken the wrong approach to the whole problem?) I do not wish to know the correct code, so that I am able to learn during the whole process of re-editing my code.
Any help (hopefully no model-code answers though), even as a single comment, is tremendously appreciated! :)
This is my code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
#include <stdbool.h>
#include <time.h>
//Pls excuse my extensive use of libraries even though I don't really use them
int intchecker(float x)
{
if (floor(x)==x && ceilf(x)==x)
{
return 0;
}
else {
return 1;
}
}
int main(){
char line[] = " +----+----+----+----+----+----+----+----+----+----+---+";
char numbers[] = " 0 5 10 15 20 25 30 35 40 45 50";
float balls,slots;
int slotarry[9],tlevel,ballnum,column,lcounter=0,slotsduplicate=1,y;//tlevel-number of levels in the triangle
srand(time(NULL));
int r;
printf("==========================================================\nGalton Box Simulation Machine\n==========================================================\n");
printf("Enter the number of balls [5-100]: ");
scanf("%f",&balls);
while (balls>100 || balls<5) {
printf("\nInput is not within the range. Please try again.");
printf("\nEnter the number of balls [5-100]: ");
scanf("%f",&balls);
}
while (intchecker(balls)==1) {
printf("\nInput is not an integer. Please try again.");
printf("\nEnter the number of balls [5-100]: ");
scanf("%f",&balls);
}
printf("Enter the number of slots [2-10] : ");
scanf("%f",&slots);
while (slots>10 || slots<2) {
printf("\nInput is not within the range. Please try again.");
printf("\nEnter the number of slots [2-10] : ");
scanf("%f",&slots);
}
while (intchecker(slots)==1) {
printf("\nHow can there be a fraction of a slot? Please re-enter slot number.");
printf("\nEnter the number of slots [2-10] : ");
scanf("%f",&slots);
}
tlevel=slots-1;
for(ballnum=1,column=0;balls>0;balls--,ballnum++,column++){
if (column%5==0){
printf("\n");
}
if (ballnum<10){
printf("[0%d]",ballnum);
}
else{
printf("[%d]",ballnum);
}
for(;tlevel>0;tlevel--){
r = rand() % 2;
if (r==0){
printf("R");
}
else {
printf("L");
lcounter++;
}
}
slotarry[lcounter]++;
tlevel=slots-1;
lcounter=0;
printf(" ");
}
printf("\n\n%s",numbers);
printf("%s",line);
char line2[] = "\n +----+----+----+----+----+----+----+----+----+----+---+";
for(;slotsduplicate<=slots;slotsduplicate++){
if (slotsduplicate<10){
printf("0%d|",slotsduplicate);
}
else{
printf("%d|",slotsduplicate);
}
y=slotarry[slotsduplicate];
if (y==0){
printf(" 0");
}
else{
for (;y>0;y--){
printf("#");
}
printf(" %d",slotarry[slotsduplicate]);
}
printf("%s",line2);
}
return 0;
}
Note:This is not completely error-free. This is just my first draft. I just wish to find out why there is an infinite loop.
Here's how I found the problem. First of all, I think it is a bit of a code smell to have a for loop without anything in the initial assignment section. Couple that with the fact that it seems to print # forever, and it looks like y has a garbage value at the beginning of the loop to print the #s.
So I ran your code in the debugger and paused it when it started printing loads of hashes. I checked the value of y and sure enough it was some unfeasibly high number.
Then I checked where y comes from and found you get it from slotarray. I printed it in the debugger and found that all the values in it were unfeasibly high or massively negative numbers. Obviously, slotarray wasn't being initialised correctly, so I looked for where it was initialised and bingo!
Stack variables (of which slotarray is one) must be explicitly initialised in C. I fixed your code with a call to memset.
The whole debugging process I have just outlined took something less than a minute.
ETA As #EOF points out, there is another bug in that slotarray is defined to contain nine slots (indexed 0 - 8) but you allow people to enter 10 slots. This is a buffer overflow bug.
Hey guys I have created a program in C that tests all numbers between 1 and 10000 to check if they are perfect using a function that determines whether a number is perfect. Once it finds these it prints them to the user, they are 6, 28, 496 and 8128. After this the program then prints out all the factors of each perfect number to the user. This is all fine. Here is my problem.
The final part of my task asks me to:
"Use a "twirly" to indicate that your program is happily working away. A "twirly" is the following characters printed over the top of each other in the following order: '|' '/' '-' '\'. This has the effect of producing a spinning wheel - ie a "twirly". Hint: to do this you can use \r (instead of \n) in printf to give a carriage return only (instead of a carriage return linefeed). (Note: this may not work on some systems - you do not have to do it this way.)"
I have no idea what a twirly is or how to implement one. My tutor said it has something to do with the sleep and delay functions which I also don't know how to use. Can anyone help me with this last stage, it sucks that all my coding is complete but I can't get this "twirly" thing to work.
if you want to simultaneously perform the task of
Testing the numbers and
Display the twirly on screen
while the process goes on then you better look into using threads. using POSIX threads you can initiate the task on a thread and the other thread will display the twirly to the user on terminal.
#include<stdlib.h>
#include<pthread.h>
int Test();
void Display();
int main(){
// create threads each for both tasks test and Display
//call threads
//wait for Test thread to finish
//terminate display thread after Test thread completes
//exit code
}
Refer chapter 12 for threads
beginning linux programming ebook
Given the program upon which the user is "waiting", I believe the problem as stated and the solutions using sleep() or threads are misguided.
To produce all the perfect numbers below 10,000 using C on a modern personal computer takes about 1/10 of a second. So any device to show the computer is "happily working away" would either never be seen or would significanly intefere with the time it takes to get the job done.
But let's make a working twirly for perfect number search anyway. I've left off printing the factors to keep this simple. Since 10,000 is too low to see the twirly in action, I've upped the limit to 100,000:
#include <stdio.h>
#include <string.h>
int main()
{
const char *twirly = "|/-\\";
for (unsigned x = 1; x <= 100000; x++)
{
unsigned sum = 0;
for (unsigned i = 1; i <= x / 2; i++)
{
if (x % i == 0)
{
sum += i;
}
}
if (sum == x)
{
printf("%d\n", x);
}
printf("%c\r", twirly[x / 2500 % strlen(twirly)]);
}
return 0;
}
No need for sleep() or threads, just key it into the complexity of the problem itself and have it update at reasonable intervals.
Now here's the catch, although the above works, the user will never see a fifth perfect number pop out with a 100,000 limit and even with a 100,000,000 limit, which should produce one more, they'll likely give up as this is a bad (slow) algorithm for finding them. But they'll have a twirly to watch.
i as integer
loop i: 1 to 10000
loop j: 1 to i/2
sum as integer
set sum = 0
if i%j == 0
sum+=j
return sum==i
if i%100 == 0
str as character pointer
set *str = "|/-\\"
set length = 4
print str[p] using "%c\r" as format specifier
Increment p and assign its modulo by len to p
I want to ask something that I write in C.
I use the fopen() command to open and read a text file that contains only two lines. in
first line is an integer N number, and in the second line is the N integer numbers that the first line says.
Eg.
-------------- nubmers.txt --------------
8 <-- we want 8 numbers for the 2nd line
16 8 96 46 8 213 5 16 <-- and we have 8 numbers! :)
but I want to take restrictions when the file openend.
the number N should be between 1 ≤ Ν ≤ 1.000.000. If not then show an error message. If the file is ok then the programm continue to run with another code.
Here is what I done until now:
int num;
....
fscanf(fp,"%d",&num); // here goes the fscanf() command
if(num<1 || num>1000000) // set restrictions to integer
{
printf("The number must be 1<= N <= 1.000.000",strerror(errno)); // error with the integer number
getchar(); // wait the user press a key
return 0; // returning an int of 0, exit the program
}
else // if everything works.....
{
printf("work until now"); // Everything works until now! :)
getchar(); // wait the user press a key
return 0; // returning an int of 0, exit the program
}
But the problem is that the restriction checks only for the first line number , it's correct though, but don't read the numbers in the second line.
What I mean is that :
Lets say that I have the number 10 in the first line.
The code will analyze the number, will check for restrictions and will proceed to the 'else' part
else // if everything works.....
{
printf("work until now"); // Everything works until now! :)
getchar(); // wait the user press a key
return 0; // returning an int of 0, exit the program
}
..and it will said that everything is working.
But what if I have 20 numbers in the second line? -when I need only 10
Eg.
-------------- nubmers.txt --------------
10
16 8 96 46 8 213 5 16 8 9 21 5 69 64 58 10 1 7 3 6
So I hoped be as cleared as I could. My question is that I need a code in the program, besides the 1st restriction, that have also another one restriction under the first that will read the second line of the txt file with the numbers and check if there are as many numbers as the first line says!
How do I do that?
If you guys want any other declarations feel free to ask!
Hope I was clear with my problem :)
This will check the number of integers and report too many or not enough. The integers are not saved except for each one being read into the value. Do you want to store each integer?
fscanf(fp,"%d",&num); // here goes the fscanf() command
if(num<1 || num>1000000) // set restrictions to integer
{
printf("The number must be 1<= N <= 1.000.000",strerror(errno)); // error with the integer number
getchar(); // wait the user press a key
return 0; // returning an int of 0, exit the program
}
else // if everything works.....
{
int i = 0;
int value = 0;
while ( fscanf ( fp, "%d", &value) == 1) { // read one integer
i++; // this loop will continue until EOF or non-integer input
}
if ( i > num) {
printf ( "too many integers\n");
}
if ( i < num) {
printf ( "not enough integers\n");
}
getchar(); // wait the user press a key
return 0; // returning an int of 0, exit the program
}
use a loop that takes the first num and checks is is the number of integers in next line:
int z = num;
while(z--){
if (getchar() == EOF)
printf("err")
}
Do it like this:
fscanf(fp,"%d",&num);
// next lines of code (restrictions). Then place the below code before getchar in the else
int temp[num+1];// space to store num integers to temp and 1 space to check for extra number
for(i=0;i<num;i++)
{
if(fscanf(fp,"%d",&temp[i]) != 1)// fscanf will automatically read 2nd line and store them in temp array
//error ! Less numbers in file !
}
if(fscanf(fp,"%d",&temp[num]==1) //if still numbers can be scanned
//Extra numbers found in line 2
i'm trying to create a 'game' in C programming which throws 2 dices for the user, throws 2 dices for the PC, and whoever gets the bigger sum wins,
when i debug it in visual studio i see good results both in the variable values and the console window, but when i run it without debugging the user and the PC both always get the same value for their dices (user gets 2 and 2, and PC gets 2 and 2, for example).
Can anyone solve it? i looked at it for the last 3 hours and i just can't find what's the problem.
#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
int throwDice();
int diceSum();
int main()
{
int res1;
res1=diceSum();
if(res1==0)
printf("It is a tie!\n");
if(res1==1)
printf("You Won!\n");
if(res1==-1)
printf("You Lost\n");
}
int throwDice()
{
int i;
srand((unsigned)time(NULL));
i = (rand()%(6-1)) + 1;
return i;
}
int diceSum()
{
int j,a=0,b,c=0,d=0;
int array[4];
for(j=1;j<=2;j++)
{
array[c]=throwDice();
a=a+array[c];
c++;
}
for(b=1;b<=2;b++)
{
array[c]=throwDice();
d=d+array[c];
c++;
}
printf("You got %d and %d.\nYour opponent got %d and %d.\n",array[0],array[1],array[2],array[3]);
if(a==d)
return 0;
if(a>d)
return 1;
else
return -1;
}
Everytime you call throwDice, you are re-initializing your random number generator with the current time.
The accuracy of time is only 1-second, so in a single run of this program, the time doesn't change, so you get the same results.
You are supposed to call srand ONLY ONCE, near the start of your program.
From the documentation
"Two different initializations with the same seed will generate the same succession of results in subsequent calls to rand."
The random number generator doesn't just pull random numbers out of nowhere. When you seed it you're giving it a good number to start with, and from there it can generate a bunch of random numbers.
The problem is, it will give you a sequence of random numbers, but that sequence will be the same if you give it the same seed twice in a row. That's why it's important that the value you seed it with is relatively random. And hey, the time is pretty random, what are the chances two people will end up running the program at exactly the same time?
What you're doing, is seeding the generator before every call to rand, instead of seeding it at the beginning and letting the random number generator do its job. Since time only returns the time in seconds (see man page), you'll get the same number every time the loop runs until the start of the next second.