Inputing integers straight across in C - c

I'm in a beginner C course and I was wondering if there's a way to input integers straight across and averages them together? I'm trying to make my program nice and tidy as possible.
I want to input integers straight across like:
Enter the temperatures and Enter 00 when finished:
60 80 97 42
Average is: 69.75
I don't want to input integers like shown below:
Enter the temperatures and Enter 00 when finished: 75
Enter the temperatures and Enter 00 when finished: 80
Enter the temperatures and Enter 00 when finished: 46
Enter the temperatures and Enter 00 when finished: 91
Average is: 73

#include <stdio.h>
#include <string.h>
int main(void){
char input[64];
double ave = 0.0, value;
int count = 0;
printf("Enter the temperatures and Enter 00 when finished:\n");
while(1){
if(1==scanf("%63s", input)){
if(strcmp(input, "00") == 0)
break;
if(1==sscanf(input, "%lf", &value))
ave += (value - ave) / ++count;
}
}
if(count)
printf("Average is: %g\n", ave);
else
printf("Input one or more values\n");
return 0;
}

Using the scanf function any white space character is seen as the end of input for each integer. Thus using scanf within a loop you can continuously input values within the same line.
If you want it to work for a different number of entries each time you must modify the code to use a while loop and have a dynamically allocated array, since the size is unknown. Then check for an escape sequence like 00.
All the values are stored into an array where you can do the averaging calculations
#include <stdio.h>
#define NUM_OF_ENTRIES 5
int main()
{
printf("Enter numbers: ");
int i = 0;
int value_set[NUM_OF_ENTRIES];
for (i = 0; i < NUM_OF_ENTRIES; i++ )
{
scanf("%d", &value_set[i]);
}

I believe that you shall change your terminating condition from enter 00 to something like enter x.
So, your code shall look like this::
int n;
int sum = 0, count = 0;
while(scanf("%d", &n)) {
sum = sum + n;
count++;
}
printf("%lf", double(sum/count));
scanf returns the number of successfully taken inputs. Since n is declared as int, so everytime you enter some integer value, scanf will return 1 and if you enter some value which is not of type int like if you enter x (which is a char) scanf will return 0, because x is not an integer, and this way you can calculate the average.

Code can use scanf("%d", &number) to read an integer. The trouble is that "%d" first scans and discards leading white-space which includes '\n' before scanning for an int. '\n' is needed to know when to stop as OP wants "input integers straight across". So instead code should look for white-space one character at a time first. Upon finding the end-of-line '\n', scanning is complete.
With this approach there are no practical limits to the count of numbers.
#include <ctype.h>
#include <stdio.h>
double Line_Average(void) {
double sum = 0;
unsigned long long count = 0;
while (1) {
int ch;
while (isspace(ch = fgetc(stdin)) && ch != '\n')
;
if (ch == '\n' || ch == EOF) {
break; // End-of-line or End-if file detected.
}
ungetc(ch, stdin); // Put back character for subsequent `scanf()`
int data;
if (scanf("%d", &data) != 1) {
break; // Bad data
}
sum += data;
count++;
}
return sum/count;
}
// sample usage
puts("Enter the temperatures");
double Average = Line_Average();
printf("Average is: %.2f\n", Average);

One possibility:
double sum = 0;
double val;
size_t count = 0;
char follow;
while( scanf( "%lf%c", &val, &follow ) == 2 )
{
sum += val;
count++;
if ( follow == '\n' )
break;
}
printf( "average = %f\n", sum/count );
This will read each number plus the character immediately following, until it sees a newline or a non-numeric string. It's not perfect; if you type a number followed by a space followed by a newline, then it won't break the loop. But it should give you some ideas.

since u did not post the code. i have given a sample code... from here u can build what u require with some tweaks
#include<stdio.h>
main()
{
int one, two, thr, four, five, avg;
printf("\nEnter the temperatures and Enter 00 when finished:");
scanf ("%d %d %d %d %d", &one, &two, &thr, &four, &five);
avg=(one+two+thr+four+five)/5;
printf("Average value is %d", avg);
}

Related

(Visual Studio)Calculation _using for sentence

Want to elicit average of entered real value,until negative value is entered.
My problem is
My calculation don't quit when negative value is entered
It keep asks printf sentence for 3 time.
What did I do wrong?
#include <stdio.h>
int main(void)
{
double total = 0.0;
double input=0.0;
int num = 0;
for (; input >= 0.0;)
{
total += input;
printf("real number(minus to quit):");
scanf_s("%1f", &input);
num++;
}
printf("average:%f \n", total / (num - 1));
return 0;
}
you have many problems with your code :
it's not %1f in the line scanf_s("%1f", &total); as %1f will give you undefined behavior , it's %lfas you are scanning a double , there is a big difference between number one and lower case L
the function called scanf returns an integer indicating how many elements could be assigned to the input that the user entered , so , you should do if(scanf_s("%lf", &input) == 1) to check if the assignment done successfully, that will help you in detecting if - is entered instead of the number
if the user entered a lonely - then sacnf will fail to convert and you have to take another approach
when you are printing the average in this line : printf("average:%f \n", total / (num - 1)); , you actually prints a double , so it's %lf instead of %f
the condition of the for loop is incorrect , you are saying for (; input >= 0.0;) but this will prevent you from entering any negative values as when entering a negative value , the for loop will break , so you could use while(1) instead of the for loop and only break when a - is entered alone
so here is my edited version of yours , I introduced a dummy string to read the buffer and check whether the input was a lonely - or not , and if not then I try to convert it to double and here is my edited solution :
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
char dummy[30];
double total = 0.0;
int num = 0;
double DecimalConverted = 0;
while(1)
{
printf("real number(minus to quit):");
fgets(dummy, 30, stdin); // gets the input into the buffer
if(dummy[0] == '-' && dummy[1] == '\n') // break from the loop on condition that '-' only entered
break;
// convert the string to decimal
DecimalConverted = strtod(dummy ,NULL);
if(DecimalConverted == 0)
printf("not a number\n");
else{
total += DecimalConverted;
num++;
}
}
printf("average:%lf \n", total / (num - 1));
return 0;
}
and here is the output :
real number(minus to quit):12
real number(minus to quit):-51
real number(minus to quit):-
average:-39.000000

C programming Luhn algorithm

I have tried to write a program in C to check Luhn algorithm for credit cards, but it doesn't work. I think I do not have quite clear how getchar() works, but this program looked sensible to me. Can you tell me what is wrong with it? Thank you in advance for any help with this.
#include <stdio.h>
int main(void) {
char x;
int n, sum, i, c;
sum = 0;
printf("Insert the number of digits: ");
scanf("%d",&n);
printf("Insert the digits: ");
for(i = n; i > 1; i = i - 1){
x = getchar();
if(i%2==0)
if(2*x < 10) sum = sum + 2*x;
else sum = sum + 2*x - 9;
else sum = sum + x;
i = i - 1;
}
c = (9*sum)%10;
x = getchar();
getchar();
if(x == c) printf("Last digit: %d,\nCheck digit: %d,\nMatching",x,c);
else printf("Last digit: %d,\nCheck digit: %d,\nNot Matching",x,c);
}
getchar() reads one character. Therefore, the x = getchar(); in the loop is not good because
It firstly read a newline character if you enter that after the first "number of digits".
It will read a character, not an integer. Character codes typically differ from the integer the character represents, and it may affect the check digit calculation.
Instead of x = getchar();, you should do this in the loop:
scanf(" %c", &x); /* ignore whitespace characters (including newline character) and read one character */
x -= '0'; /* convert the character to corresponding integer */
#include <stdio.h>
#define N 16
void luhn_algorithm();
int main(){
int a[N];
int i;
printf("type the card number:\n");
for(i=1;i<=N;i++){
scanf("%d",&a[i]);
}
luhn_algorithm(a);
}
void luhn_algorithm(int *a){
int i,multiply=1,m,sum=0,total=0;
for(i=1;i<=N;i++){
if(i%2!=0){
multiply=a[i]*2;
if(multiply>9){
while(multiply>0){
m=multiply%10;
sum+=multiply;
multiply/=10;
}
multiply=sum;
}
}
else if(i%2==0){
multiply=a[i]*1;
if(multiply>9){
while(multiply>0){
m=multiply%10;
sum+=multiply;
multiply/=10;
}
multiply=sum;
}
}
total+=multiply;
}
if(total%10==0){
printf("\nthis credit card is valid ");
}
else{
printf("\nthis credit card is not valid");
}
}
this is the program i made to check if credit card number is valid or not try this out.
I took the numbers in an array and then multiplied it according to their position and added them all if the last digit of the added total comes out to be 0 that means the card is valid otherwise its not.
check it out if theres something wrong please tell me.

Isalpha is requiring an identifier

Here's my code:
#include <stdio.h>
#include <ctype.h>
main(){
float input;
printf("Input: ");
scanf("%f", &input);
if (isalpha(input) || (input) < 0)){
printf("Input is an alphabet or is lesser than 0");
} else {
printf("Input is correct. %f is a number larger than 0", input);
}
}
I want the code to detect if input is a number larger than 0, or is it an alphabet. However, I am getting this error:
8: error: identifier expected
What does it mean to my code's execution? How am I supposed to run the code successfully?
Correct parentheses in if:
if ( isalpha(input) || (input < 0) )
In addition, you need to check the return value of scanf() whether there was input or not. In the case of no input, the return value would be 0 or in case of multiple inputs how many succeeded. In your case, you can use the return value to determine whether a float was input or not.
The main() should return an int and always initialize your variables.
Example (live):
#include <stdio.h>
#include <ctype.h>
int main()
{
float input = 0.0f;
printf("Input: ");
int ret = scanf("%f", &input);
if ( ret == 0 )
{
printf("ERROR: Input is NOT a float!\n");
return -1;
}
if ( input < 0.0f )
{
printf("Input is less than 0");
}
else
{
printf("Input is correct. %f is a number larger than 0", input);
}
return 0;
}
Your parentheses aren't opened/closed properly.
Maybe your ide/compiler is taking care of it, but it should be int main()
isalpha() will behave unexpectedly with float values. Try avoiding that.
First of all you are missing int declaring main,
int main()
Also,you have excessive bracket in line
if (isalpha(input) || (input) < 0)){
Scanf uses %f to read floats. What your program will do is accept any ascii character and I suppose that wasn't your intention.
I am still not sure what you need, but you could try something like this as a starting point. It does not handle all possible inputs, and will erroneously classify an input such as #42 as alphabet or lesser than 0, which is questionable, but you can iterate on this and hopefully get to a more polished version.
#include <stdio.h>
#include <ctype.h>
int main(){
float input;
printf("Input: ");
if (scanf("%f", &input) && input >= 0){
printf("Input is correct. %f is a number larger than 0", input);
} else {
printf("Input is an alphabet or is lesser than 0");
}
}
Explanation
We save the value in input, if compatible with the %f format:
float input;
Prompt for the user:
printf("Input: ");
This condition is made of two parts; the first part is the scanf, that will try to read input, and if successful will evaluate to 1, which is true, so the second part input >= 0 will be evaluated, and if input is indeed >= 0 we print the first message.
if (scanf("%f", &input) && input >= 0){
printf("Input is correct. %f is a number larger than 0", input);
Else we print the second message.
} else {
printf("Input is an alphabet or is lesser than 0");
}

Scanning Values Until Getting a Significant Character in C

For my homework, I am trying to code a calculator which can also calculate average of taken numbers. I don't want to ask for number of numbers because our teacher don't want it in that way. So I thought of scanning values until the user presses "p". But as you would guess, the numbers are float and "p" is a character. What I want to do is assigning the value scanned to both of them if it is possible. I tried different ways, played with the codes but it isn't working properly. So I am seeking your advice.
It prints a value when p is inputted as like 3rd, 5th, 7th (oddth) number (sometimes right, sometimes wrong but I can fix it if I figure this out). But it doesn't print a value in other occasions and expects infinite inputs from the user.
This is the code I have written for this. scanf("%f %c", &number1, &pause); command is where I want to know about, actually.
#include<stdio.h>
float number1, number2, i, result;
char pause;
int main() {
scanf("%f", &number1);
i = 0;
while (pause != 'p') {
number2 = number1 + number2;
scanf("%f %c", &number1, &pause);
i++;
}
result = number2 / (i - 1);
printf("%f", result);
}
Use double not floats if there is no specific reason to do so (like using uC without double FPU).
You do not initialize the variables
Always check the result of the I/O operation.
#include <stdio.h>
int main ()
{
double number1= 0, number2 = 0, i = 0, result = 0;
char pause = 0;
char line[128];
while (pause != 'p')
{
if(fgets(line, sizeof(line), stdin))
{
if(sscanf(line, "%lf %c",&number1, &pause) != 2)
{
printf("Wrong input - try again\n");
pause = 0;
continue;
}
number2 = number1 + number2;
i++;
}
else
{
// do something with I/O error
}
}
result = number2 / (i-1);
printf("%lf",result);
}
You can play with it yourself : https://onlinegdb.com/Hy3y94-3r
I noticed 3 problems with your code.
First I would advise you to use meaningful variables names. number1, number2, etc. and the i which represents the number of inputs given can be an int instead of a float.
Secondly, you lack of printing to the user what's going on in your program; it's better to have messages like "enter your number, do you wanna stop? the result is...etc".
Lastly, having two inputs in one line of code can make it hard to debug, knowing that reading strings and characters in C is already hard for beginners. For example, %c does not skip whitespace before converting a character and can get newline character from the previous data entry.
Here is my fix: I changed some variables' names, printed some messages and read the two inputs in two different lines with adding scanf(" %c") with the space to avoid that problem.
#include<stdio.h>
float sum, temp, result;
int nb;
char pause;
int main () {
pause='a';
while (pause != 'p'){
printf("Enter your number: ");
scanf("%f",&temp);
sum+=temp;
nb++;
printf("type 'p' if you want to stop: ");
scanf(" %c",&pause);
}
result = sum / nb;
printf("the average is : %f",result);
}
I tested it, should work fine
Edit: after explaining that you don't want to ask the user each time, here is how the code should work (the case that the user don't input a float is not treated, and just take it as zero
#include<stdio.h>
#include<string.h>
#include <stdlib.h>
float sum, temp, result;
int nb;
char input[50];
int main () {
sum=0;
nb=0;
printf("Enter your numbers, then type 'p' to stop\n");
do{
printf("Enter your next number: ");
scanf("%s", input);
if(strcmp(input,"p")!=0)
{
float temp= atof(input);
sum+=temp;
nb++;
}
}while(strcmp(input,"p")!=0);
if(nb!=0)
result = sum / nb;
printf("\nThe average is : %f",result);
}

Writing a program to find the largest in a series of numbers.

I am very new to C. I am using A modern Approach to C programming by King 2nd Edition.
I am stuck on chapter 6. Question 1: Write a program that finds the largest in a series of numbers entered by the user. The program must prompt the user to enter the numbers one by one. When the user enters 0 or a negative number, the program must display the largest non negative number entered.
So far I have:
#include <stdio.h>
int main(void)
{
float a, max, b;
for (a == max; a != 0; a++) {
printf("Enter number:");
scanf("%f", &a);
}
printf("Largest non negative number: %f", max);
return 0;
}
I do not understand the last part of the question, which is how to see which non-negative number is the greatest at the end of user input of the loop.
max = a > a ???
Thanks for your help!
So you want to update max if a is greater than it each iteration thru the loop, like so:
#include <stdio.h>
int main(void)
{
float max = 0, a;
do{
printf("Enter number:");
/* the space in front of the %f causes scanf to skip
* any whitespace. We check the return value to see
* whether something was *actually* read before we
* continue.
*/
if(scanf(" %f", &a) == 1) {
if(a > max){
max = a;
}
}
/* We could have combined the two if's above like this */
/* if((scanf(" %f", &a) == 1) && (a > max)) {
* max = a;
* }
*/
}
while(a > 0);
printf("Largest non negative number: %f", max);
return 0;
}
Then you simply print max at the end.
A do while loop is a better choice here because it needs to run at least once.
#include<stdio.h>
int main()
{
float enter_num,proc=0;
for(;;)
{
printf("Enter the number:");
scanf("%f",&enter_num);
if(enter_num == 0)
{
break;
}
if(enter_num < 0)
{
proc>enter_num;
proc=enter_num;
}
if(proc < enter_num)
{
proc = enter_num;
}
}
printf("Largest number from the above is:%.1f",proc);
return 0;
}

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