I really need help to store double values in a double array. I am trying using scanf_s and it works. But if I try to input more than 4 values, my program crashes and returns me the error code 3
I actually need a dynamic array, but as I was getting too many errors with that, I changed and I'm trying to use a common array, just so I can get at least some marks for this project.
This is the code I am using now...
int main()
{
printf("Enter white-space separated real numbers. Terminate input with ^Z\n");
//get the dynamic array
double numSet[1000] = { 0 };
int size = 0;
double number;
while (scanf_s("%lf", &number) == 1)
{
numSet[size] = number;
size++;
}
//sort the array using qsort
//range of the array
double min = numSet[0];
double max = numSet[size - 1];
//get the mean
double sum = 0.0;
for (size_t i = 0; i < size; i++)
{
sum += numSet[i];
}
double mean = sum / size;
printf("Range: [%.2f ... %.2f]\n", min, max);
printf("Arithmetic mean is: %f", mean);
}
I have two problems:
Is a warning about buffer overrun:
Warning C6385 Reading invalid data from 'numSet':
the readable size is '8000' bytes, but '-8' bytes may be read.
When I try to input more than 4 numbers, my program crashes and returns the code 3
while (scanf_s("%lf", &number) == 1)
{
numSet[size] = number;
size++;
}
instead of this use
while (scanf_s("%lf", &number) == 1 && size <= 1000)
{
numSet[size] = number;
size++;
}
Your loop goes infinitely because it has no termination character.
scanf_s only reads value from keyboard and has another parameter to set its maximum input buffer value which is useful to limit your input.
What you can do is either read size from the user before letting him enter values or you can ask every time if the user wants to add more values to the array or not.
for example:
char option = 'Y';
while ( (scanf_s("%lf", &number) == 1 && option == 'Y'){
// code to enter a new number
printf("Do you want to add more numbers? (Y/N) ");
scanf("%c", &option);
}
Also, the scanf_s function returns the number of values scanned and every time is 1 as you are always taking one double value.
So even if you remove it, it wont be of much trouble.
I think the problem is how you end the input loop, scanf_s isn't needed, please see the watch window. I simply change the end condition to some no digit char.
Code::Blocks watch window
As mentioned in the comments, it's possible for
double max = numSet[size - 1];
to evaluate as
double max = numSet[-1];
when size = 0. I'm guessing that a double is 8 bytes wide, so the compiler warns that it could try to read -1 * 8 = -8 bytes from memory.
Related
I was trying to make a 'decimal to binary' program. It should convert from 0 to 255 only and it does.
I have two variables, 'n' and 'temp', when the user first enters the number I store it on 'n'. Then I assign 'n' to 'temp' (thus creating a copy, at least that's what I think I'm doing).
then I only use 'temp' in my code. I never use 'n', not until the end where I decide to print the number the user entered. And here comes the problem, if I enter a number greater than 255, the variable 'n' changes to 1.
I tried running my code through a couple C online compilers and all of them output the variable 'n' the right way, meaning that despite the binary not working when the numbers is greater than 255 (as intended) they print the entered value.
I found one online compiler where it doesn't print the 'n' variable if its greater than 255.
https://www.tutorialspoint.com/compile_c_online.php
If you run my code through this compiler, you'll see how the variable 'n' changes to 1 without it being used.
I know the 'binary part' won't work if you use a number greater than 255. I want to know why 'n' changes out of nowhere.
#include <stdio.h>
int main()
{
int bin[8] = {0, 0, 0, 0, 0, 0, 0, 0};
int arrSize = 7;
int n;
int temp;
scanf("%d", &n);
temp = n;
while(temp != 0)
{
bin[arrSize] = temp % 2;
temp = temp / 2;
arrSize = arrSize - 1;
}
printf(" Decimal: %d ----> binary: ", n);
for(int i = 0; i <= 7; i++)
{
printf("%d", bin[i]);
}
printf("\n");
return 0;
}
You've run through a "Buffer overflow".
A quick definition for that:
A buffer overflow occurs when a program or process attempts to write
more data to a fixed length block of memory, or buffer, than the
buffer is allocated to hold. Since buffers are created to contain a
defined amount of data, the extra data can overwrite data values in
memory addresses adjacent to the destination buffer unless the program
includes sufficient bounds checking to flag or discard data when too
much is sent to a memory buffer.
The error in your code remains in this while loop:
while(temp != 0){
//I added this line to make it clear
printf("inside loop\tarrSize=%d\n",arrSize);
bin[arrSize] = temp % 2;
temp = temp / 2;
arrSize = arrSize - 1;
}
For an input equals to 300 (The error will occur for each input > 255) you'll have this output:
inside loop arrSize=7
inside loop arrSize=6
inside loop arrSize=5
inside loop arrSize=4
inside loop arrSize=3
inside loop arrSize=2
inside loop arrSize=1
inside loop arrSize=0
inside loop arrSize=-1
inside loop arrSize=0
The problem is that we have an index equals to -1, You'll ask what will happen ? well in fact arrays are pointers to the address of the first element of the table + the offset (index * size of the type of the table) which means that for bin[-1] it is in fact arrSize, and bin[-2] is in fact n.
You can check this by verifying the addresses as it follows:
printf("# of bin[-1]:\t%p\n",(void*)&bin[-1]);
printf("# of arrSize:\t%p\n\n",(void*)&arrSize);
printf("# of bin[-2]:\t%p\n",(void*)&bin[-2]);
printf("# of n:\t\t\t%p\n",(void*)&n);
which with my compiler gave me:
# of bin[-1]: 0x7ffe00e32f9c
# of arrSize: 0x7ffe00e32f9c
# of bin[-2]: 0x7ffe00e32f98
# of n: 0x7ffe00e32f98
So you changes without knowing bin[-1] (or bin[-2] according to the value of n) which is in fact arrSize (or n)..
How you can fix this ? I advice you to verify the index every time you want to loop over an array (the condition of the loop must be in function of arrSize). Or you can if you want for this specific exemple to ignore that and focus on the logic: verify the input (in your case the input n must be: 0 <= n <= 255)
void *ieee2b(double value,char size,void *res){
char
*p0=res,
*p=p0;
vbreplacec(vbsprintf(p,"%*.*s",size,size," "),' ','0',p);
if((long)value!=value)
while(1){
double
tmp=value*2;
*p++='0'+(long)tmp;
if(tmp==1||tmp==0||p-p0>size)
break;
value=tmp-(long)tmp;
}
else{
p=p0+size-1;
while((long)value>1){
*p--='0'+((long)value%2);
value=(long)value/2;
}
*p--='0'+((long)value);
}
return res;
}
I'm just starting learning C but I really don't know what am I doing wrong. I wrote this code, and it was supposed to stop reading numbers when it receives a negative number. I have wasted a lot of time trying to figure out what it is wrong, and I still don't know what it is.
#include<stdio.h>
int main(){
const int qtd = 3;
float ent[qtd];
int i = qtd;
printf("Digite os numeros\n");
do{
scanf("%f", &ent[i]);
i--;
}while (ent[i] >= 0 && i >= 1);
printf("\n\n\n\nPressione 'Enter' para sair");
fflush(stdin);
getchar();
return 0;
}
The problem is with the index of ent that you check for being negative. It's ent[i], but it is after i has been decremented, so you are reading the location that has not been written yet by scanf.
To fix the problem, change the code to use the prior location, i.e.
do {
...
} while (ent[i+1] >= 0 && ...);
There are several other problems with your code, all coming from the assumption that array indexes start at 1. In C, however, the initial index is zero, not one, so the correct check should be
do {
...
} while (ent[i+1] >= 0 && i >= 0);
In addition, i should be initialized to int i = qtd-1; to avoid writing past the end of allocated array.
I've been pouring over my code (which does not work) now for quite some time. It is for a Project Euler problem in which one is given a very large sum to find, and then required to print the first ten digits of said sum. (The problem can be found here: https://projecteuler.net/problem=13)
I have run several 'tests' where I add print commands to see various values at various points in the code. When I run the code, I have gotten anything from symbols to ten digit numbers that should be single digits.
Anyways. My question is this: is this a type conversion issue or is there some other glaring issue with my method that I'm missing? I've been studying type conversions trying to find a fix, but to no avail.
Thank you for any help!
The code is as follows:
// this is a program to find a very large sum of many very large numbers
#include <stdio.h>
#include <math.h>
int main()
{
//declare all ints needed
int i;
int j;
int d; // digit, need to add 48
int placesum; // sum of addition in _'s place (1's, 10's, 10000's)
int place; // final place value
int c = 0, tens = 1, otherc; // counters for start finder
int a = 0; // another counter
//declare all arrays
char numarray[101][51]; //array of strings containing all 100 numbers
char sum[100];
printf("please save data to largesumdata.txt\n\n press enter when ready");
getchar();
// THE PROBLEM- I don't know how to get my data into my program // FIXED
// using fscanf()
FILE *pf; // declare a pointer to the file
pf = fopen("largesumdata.txt", "r"); // trys to open file // "r" means read only
if(pf == NULL)
printf("Unable to open file, sorry Jar\n");
else
{
for(j = 0; j < 100; j++)
fscanf(pf, "%s\n", &numarray[j]); // fscanf(pointer, data type, location)
}
//TESTING
//printf("You have reached point A\n");//POINT A WAS REACHED
//TESTING
//TESTING
//printf("Check1, %c\n", numarray[45][23]);
//TESTING
//TESTING
//printf("%c\n", numarray[90][22]);//Can successfully call characters from array
//TESTING
// (Brute force attempt) //I NEVER MESS WITH numarray WHY IS IT CHANGING
for(i = 49; i >= 0; i--)
{
//printf("%d\n", d);
for(j = 0; j < 100; j++)
{
d = (int)numarray[j][i] - 'o';
//printf("%d\n", d);
//holdup// d -= 48; // ASCII conversion // could also write "d = d-48"
//printf("%d\n", d);
placesum += d; // could also write "placesum = placesum + d"
//printf("%d\n", placesum);
}
place = placesum % 10;
placesum = placesum / 10; // takes "10's place" digit for next column
// now need to put 'int place' into 'char sum'
sum[i+5] = (char)place+'0'; // ASCII conversion // "+5" for extra space //HERE not properly stored in sum
}
//TESTING
//printf("Check2, %c\n", numarray[45][23]);
//TESTING
//TESTING
//printf("You have reached point B\n");//POINT B WAS REACHED
//TESTING
// find out where sum starts
for(c=0; c<10; c++)
if(sum[c] != '0')
break;
//TESTING
//printf("You have reached point C\n"); //POINT C WAS REACHED
//TESTING
otherc = 4-c;
printf("The first 10 digits of the sum of all those f***ing numbers is....\n");
printf("%d-%d-%d-%d-%d-%d-%d-%d-%d-%d", sum[otherc, otherc+1, otherc+2, otherc+3, otherc+4, otherc+5, otherc+6, otherc+7, otherc+8, otherc+9]);
//%c-%c-%c-%c-%c-%c-%c-%c-%c-%c //copy and paste purposes
//%d-%d-%d-%d-%d-%d-%d-%d-%d-%d // ^^^^^
getchar();
return 0;
}
P.S. I apologize if my plethora of notes is confusing
You are using wrong form to print an array in C.
sum[otherc, otherc+1, otherc+2, otherc+3, otherc+4, otherc+5, otherc+6, otherc+7, otherc+8, otherc+9] -> This actually decays to sum[otherc+9] because C treats , as an operator.
To print value at each array index, you should use it like this: sum[otherc], sum[otherc+1], sum[otherc+2],..
To read more about C's , (comma) operator, you can begin here
In your printf as I explained above, the first format specifier %d gets sum[otherc + 9], since sum[otherc,...,otherc+9] is actually a single number and that is otherc + 9th index of array sum. You do not provide anything to print for other format specifiers, hence you get garbage.
After a while I revisited my code, and realized that I was working with numbers upwards of 10 million. I had a mix of int, long int, and long long int variables declared.
I re-analyzed which was which, and made sure that all variables could handle the data it needed to (after looking at this handy link, showing what max integer sizes are for different data types.
Before I had been using the wrong ones, and going over the max values returned incorrect values, causing my program to crash during run time.
Lesson here: Check your data types!
I am trying to make a program that allows the user to input a positive integer, and the program will output the sum of each digit added together. For example, if the user inputs 54, the program will output 9. For some reason, the program is outputting outrageously huge numbers. When 54 is the input, the output will read something like 5165451 or 2191235. I'm new to C programming, but I don't see a single thing wrong with this code..
//This program takes a positive integer
//from the user, and adds all the digits
//of the number together.
#include <stdio.h>
int main() {
system("clear");
int given, add, hold, i;
printf("Enter a positive integer (up to 10 digits): ");
scanf("%d", &given); //User input
for (i = 0; i < 10; i++) { //Loop to add digits
hold = (given % 10);
given = (given / 10);
add = (add + hold);
}
printf("Sum of the digits is %d\n", add); //Output
}
int given, add, hold, i;
You haven't initialized add, so it contains unspecified data, aka garbage. Using its value while it is unspecified is undefined behaviour.
Insert add = 0; before the loop to see if that helps.
I think the for loop is wrong
The loop will run 10 times whereas scanf will only take the input upto the limit of int data type i.e 32768.
You should make given a long data type.
and make the for loop as
for(;given!=0;)
{
hold = (given % 10);
given = (given / 10);
add = (add + hold);
}
and of course initialize add to zero.
This is a homework project I was assigned some time ago... I've been successful in getting this far on my own, and the only hiccup I have left is (I believe) an issue with data types and overflow.
I've tried changing over to unsigned and double, and the code complies and still accepts input in the terminal, but it seems to hang up after that... nothing is printed and it looks like it's caught in a loop.
Here is the code...
/* pascaltri.c
* A program that takes a single integer as input and returns the nth line of
* Pascal's Triangle. Uses factorial() function to help find items of
* individual entries on a given row.
*/
#include <stdio.h>
#include <stdlib.h>
long factorial(long i)
{
long fact = 1;
while(i > 1)
{
fact = fact * i;
i = i - 1;
}
return fact;
}
main(void)
{
long n;
long *nPtr;
nPtr = &n;
scanf(" %i", nPtr);
if (n >= 0)
{
long k;
long *kPtr;
kPtr = &k;
for(k = 0; k <= n; k++)
{
long ans;
long *ansPtr;
ansPtr = &ans;
ans = factorial(n) / (factorial(k) * factorial(n - k));
printf("\n %i", ans);
}
return 0;
}
return 0;
}
It's not perfect or pretty, but it works up to an input of 13 (that is, row 14) of the triangle. Beyond that I start getting gibberish and even negative values sprinkled throughout the returns... much larger values break the code and return nothing but an exit error message.
Any ideas on how I can correct this problem? I've been staring at the screen for much to long to really see anything myself. Also, it's not essential, but I would like to print my return values on one line, rather than having them separated by a newline character.
1 5 10 10 5 1
Would the easiest way be to load the values into an array as they are computed, and then print the array? Or is there a built-in way I can tell the print statement to occur on only one line?
You are suffering from integer overflow. You may need to find a different approach to the algorithm to avoid having to calculate the large numbers.
In answer to your other point about the newline, you are explicitly printing the newline with the \n in your print statement. Remove it, and you will get answers printed on one line. You probably want to inlucde a final printf("\n"); at the end so the whole line is terminated in a newline.
Some other observations:
You don't need the first return 0; - the control will drop out of
the bottom of the if block and on to the second (should be only)
return 0; and not cause any problems.
You're declaring kPtr but not using it anywhere
You don't need to declare a separate variable nPtr to pass to scanf; you can pass &n directly.
For the garbage, you are most likely running into an integer overflow, that is, your calculated values become too large for the long data type. You should correct it by calculating your factorial function without explicitely calculating n!.
Change scanf(" %i", nPtr); to
scanf(" %ld", nPtr);
and printf("\n %i", ans); to
printf("\n %ld", ans);
to get printout on one line, use:
printf(" %ld", ans);
If you are using gcc, turn on warnings, i.e. use -Wall.