I have to take a university course on C and I shall read in some integers with a while loop. The code is:
#include <stdio.h>
#define max 100
int main(){
int a[max];
int i,n;
printf("Enter the number of persons: ");
do{
scanf("%i", &n);
}while((n < 1) || (n > max));
i = 0;
while (i < n){
printf("Enter the age of the %i th Person", i+1);
scanf("%i", &a[i]);
i = i + 1;
}
/* further code */
It compiles (with the gcc compiler), but as soon as I get into the loop, it reads in the numbers correctly, but after the last input, nothing is executed anymore.
Initialise i
int i = 0;
int n;
[edit: I see now that you have edited your code as I suggested]
Initialize i = 0
Here is the working code.
#define max 5
int main()
{
int a[max];
int i = 0,n;
printf("Enter the number of persons:\n");
do{
scanf("%d", &n);
}while((n < 1) || (n > max));
while (i < n){
printf("Enter the age of the %i th Person:\n", i+1);
scanf("%i", &a[i]);
i = i + 1;
}
return 0;
}
i has a garbage value at first you should write i=0 at first
and than scanf("%d", &n); Because you are calling a while loop with a garbage value of i at the beginning and code executes if the belove statistics satisfied while((n < 1) || (n > max)) but i has no value so you do not increment it. Think about sum,count I'm sure you know what i mean. if you want to increment something you should define first. An integer i defined with no value cant increment. Use for loop at last loop, instead of while
Related
I just started learning C language. So, I am running into a lot of problems. I thought declaring i under for loop is enough, and I can use the value of i for outside too. But I think, that was not the case. Can someone explain the situation, please.
# include <stdio.h>
int main(void)
{
int x;
printf("Enter how many numbers in arrays you want to input : ");
scanf("%i", &x);
int score[x];
for(int i= 0; i <= x; i++)
{
printf("Enter the score : ");
scanf("%i", &score[i]);
}
// in the below line the output said "i" is undeclared.
float average = score[i] / x;
printf("The average score is : %f", average);
}
The answer is fairly simple
because of where you decalred i it is only visable to the for loop.
To make i visable to the whole function all you need to do is:
int i = 0;
for (; i <=x; i++){
printf("Enter the score : ");
scanf("%i", &score[i]);
}
this makes i avaliable throughout the function
i is declared in the initialization section of a for statement. That means the scope and lifetime of that variable is the expressions in the for statement itself as well as the block statement it contains. Once the loop is done, the variable no longer exists.
You need to declare i outside of the loop if you want to use it outside of the loop.
int i;
for(i= 0; i <= x; i++)
That being said, you don't actually need to use i outside of the loop.
There are security issues associated with using scanf so don't use it for anything serious. That said, I tried to re-write your program properly, and it still has pretty rubbish input validation.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INPUTTEXTLEN 20
#define MAXINPUTINT 1000
int inputint() {
char inputtext[INPUTTEXTLEN + 1] = {0};
long inputval;
while (1) {
fgets(inputtext, INPUTTEXTLEN, stdin);
if (strlen(inputtext) > 0) {
inputval = atoi(inputtext);
if ((inputval < MAXINPUTINT) && (inputval >= 0)) break;
}
}
return (int)inputval;
}
int main(void)
{
int x = 0;
printf("Enter how many numbers in arrays you want to input : ");
//scanf("%i", &x);
while (x <= 0) {
x = inputint();
}
int score[x];
float average = 0;
for(int i= 0; i < x; i++)
{
printf("Enter the score : ");
//scanf("%i", &score[i]);
score[i] = inputint();
average += score[i];
}
average /= x;
printf("The average score is : %f\n", average);
}
I've searched for solutions to that problem and couldn't find any that match mine.
I wrote a program that gets two arrays of integers and return the scalar product between them. It works fine when I'm submitting the input manually, but when I try to read the input from a text file, I encounter that Segmentation fault.
Edit: I'm talking about stdin redirection
I would be grateful for some help.
The code is:
#include <stdio.h>
#define MAXLIMIT 100
int scalar_product(int[], int[], int);
void set_array(int[]);
int main(){
int arr1[MAXLIMIT], arr2[MAXLIMIT];
int size, result;
set_array(arr1);
set_array(arr2);
printf("Enter the vectors' dimension: ");
scanf("%d", &size);
result = scalar_product(arr1, arr2, size);
printf("The scalar product is: %d \n", result);
return 0;
}
void set_array(int a[]){
int i;
printf("Please enter a vector with up to %d elements: \n", MAXLIMIT);
for (i = 0; i < MAXLIMIT - 1 && (scanf("%d", &a[i]) != EOF); i++);
}
int scalar_product(int a1[], int a2[], int size){
int product = 0, i;
for (i = 0; i < size; i++){
product += a1[i] * a2[i];
}
return product;
}
and the text file contains:
1 -2 3 -4
6 7 1 -2
4
HEre
void set_array(int a[]) {
int i;
printf("Please enter a vector with up to %d elements: \n", MAXLIMIT);
for (i = 0; i < MAXLIMIT - 1 && (scanf("%d", &a[i]) != EOF); i++);
}
When reading from the console you will never hit EOF (unless you enter ctrl-D which I guess you didnt) so your set_array loops just keep going, reading from the file. You read all the data in the first set_array and read nothing in the second one because you have finished the input file
the actualk failure was that you ran off the end of the file, so the scanf of size failed and you were trying to read a random sized array in the function scalar_product.
Test the return from scanf always
What you need to do is put a count in the file before the first array so you know how many items to read into arr1 and I suggest a count before the second lot too.
ie
void set_array(int a[]) {
int i;
int count = 0;
printf("Please enter how many elements you want to enter, max = %d \n", MAXLIMIT);
scanf("%d", &count);
if(count > MAXLIMIT) count = MAXLIMIT;
for (i = 0; i < count && (scanf("%d", &a[i]) != EOF); i++);
}
When the first number is 1 and second number is 2, and the length is 5, it should be 1 2 3 5 8. But then my output is always 1 2 1 3 4. I can't seem to find the problem.
Another input is 2 and 5. Output is 2 5 1 6 7. The 3rd number which is 1 shouldn't be there. What should I change or add?
*This is already a submitted HW and yes its wrong I got the deductions already. Now I just want to fix this so I can study this.
int main()
{
int i, lenght = 0, fib, sum, sum1, sum2, a, b, c;
printf("\nFirst number: ");
scanf("%d", &a);
printf("\nSecond number: ");
scanf("%d", &b);
printf("\nHow long?: ");
scanf("%d", &lenght);
{
while ((a > b) || ((lenght < 2) || (lenght > 100)))
{
printf("\nFirst number: ");
scanf("%d", &a);
printf("\nSecond number: ");
scanf("%d", &b);
printf("\nHow long?: ");
scanf("%d", &lenght);
}
}
printf("%d\t%d\t", a, b);
printf("%d\t", fib);
for (i = 3; i < lenght; i++) {
if (i <= 1) fib = i;
else {
a = b;
b = fib;
fib = a + b;
}
printf("%d\t", fib);
}
}
The first time you print fib (before the for loop), you haven't assigned it anything yet.
Since this is for study, issues with your code: you don't need to duplicate the calls to scanf(), simply initialize one of the variables to fail (which you did: lenght = 0) and let the loop do its thing; pick one indentation style and stick with it; if you're new to C, always include the curly braces, even when the language says they're optional; you (correctly) allow for a length of 2, but then print three numbers; your if (i <= 1) clause is a no-op as the loop starts with for (i = 3; so i is never less than 3.
Putting it all together, we get something like:
#include <stdio.h>
int main() {
int length = 0, a, b;
while (length < 2 || length > 100 || a > b ) {
printf("\nFirst number: ");
(void) scanf("%d", &a);
printf("\nSecond number: ");
(void) scanf("%d", &b);
printf("\nHow long?: ");
(void) scanf("%d", &length);
}
printf("%d\t%d\t", a, b);
for (int i = 2; i < length; i++) {
int fib = a + b;
printf("%d\t", fib);
a = b;
b = fib;
}
printf("\n");
return 0;
}
Note that the input error checking isn't sufficient to prevent problems. E.g. b can be greater than a, but still mess up the sequence if you input random numbers. You're assuming the user knows to put in two adjacent items from fibonacci sequence which is tricky to test.
just add fib=a+b; before printing fib value.
Its a good coding habit to initialize all variable before using it(especially in C).
Your code seems strange to me. I tried to simplify your code a bit. See this once:
int main()
{
int a,b,next,last,i;
printf("Enter the first Value:");
scanf("%d",&a);
printf("Enter the second Value:");
scanf("%d",&b);
printf("Enter the length of Fab. series:");
scanf("%d",&last);
printf("%d,%d,",a,b);
for (i=3; i<= last; i++)
{
next = a + b;
if(i<last)
printf("%d,",next);
else
printf("%d",next);
a = b;
b = next;
}
return 0;
}
Hope it's Helpful!!
Well it is a problem about finding the biggest and smallest number in a group of numbers, but we do not know how many numbers the user wants-
So far this is what i have done:
#include <stdio.h>
#include <conio.h>
int main()
{
int num;
int i;
int maxi=0;
int minim=0;
int cont = 0;
printf ("\nQuantity of numbers?: ");
scanf ("%d", &num);
while (num>0)
{
printf ("\nEnter number:");
scanf ("%d", &i);
if (num>i)
minim=i++;
else
if (i>num)
max=i++;
cont++;
}
printf ("\nBiggest number is es: %d", maxi);
printf ("\nSmallest number is: %d", minim);
getch();
return 0;
}
I did my program to ask how many numbers the user will want to put and i made the program to read them, BUT when it reads the biggest or/and smallest numbers it will sometimes changes biggest with small and it will not read negative numbers.
How do i do to make my program better?
You're comparing against the wrong values.
do
{
printf("Enter a number.\n");
scanf("%i", &input);
if min > input
min = input
if max < input
max = input
} while (input > 0);
#include <stdio.h>
#include <conio.h>
#include <limits.h>
int main(){
int num;
int i;
int maxi=0;
int minim=INT_MAX;
int cont = 0;
printf ("\nQuantity of numbers?: ");
scanf("%d", &num);
if(num > 0){
while (num>0){
printf ("\nEnter number:");
if(scanf("%d", &i) == 1 && !(i<0)){
if(minim > i)
minim = i;
if (maxi < i)
maxi = i;
++cont;
--num;
} else {
//fprintf(stderr, "redo input!\n")
;
}
scanf("%*[^\n]%*c");
}
printf ("\nBiggest number is : %d", maxi);
printf ("\nSmallest number is : %d\n", minim);
}
getch();
return 0;
}
You should initialize mini to the largest possible int, i.e. INT_MAX and maxi to the smallest possible int, i.e., INT_MIN. This way, even if the first number is negative, it will be considered for maxi, and if the first number is positive it will still be considered for mini. The constants INT_MAX and INT_MIN are included in <climits> or <limits.h>.
Also, you are comparing the current entered number with num, which is the counter of numbers entered by user, not one of the values he wants to compare. A better modified code would be :
#include<limits.h>
#include<stdio.h>
int main()
{
int num;
int maxi=INT_MIN; //initialize max value
int mini=INT_MAX; //initialize min value
int temp;
scanf("%d", &num); //take in number of numbers
while(num--) //loop "num" times, num decrements once each iteration of loop
{
scanf("%d", &temp); //Take in new number
if(temp>maxi) //see if it is new maximum
maxi=temp; //set to new maximum
if(temp<mini) //see if new minimum
mini=temp; //set to new minimum
}
printf("\nMaxi is:\t%d\nMini is:\t%d\n", maxi, mini); //print answer
return 0;
}
I'm trying to write a simple program that'll prompt the user to enter N numbers, store them in an array, then just sum them all up
I understand I can just do this with a recursion but I'm trying to learn how array works
Example:
1 (hit enter)
2 (hit enter)
...
10 (hit enter)
Expected output: 55
#include <stdio.h>
int main (void){
int n;
int a[n];
int counter;
printf("How many numbers do you want to enter? \n");
scanf("%d", &n);
printf("OK! now enter your number: \n");
for (int i = 0; i <= n; i++){
scanf("%d", &a[i]);
counter =+ a[i];
}
printf("The answer is: %d\n", counter);
return 0;
}
Right now there's no error message, no output, just the standard windows error message
"scanner.exe has stopped working..."
I'm using Win8 and GCC compiler
First of all, you can't create an static array without first knowing its size. You first need to ask the user for the "n" variable and then declare your array.
You also need to explicitly initialize your counter variable to be zero before you start counting. In C, variables don't default to 0 when you declare them.
The operator "=+" doesn't exist AKAIK, change it to "+=".
Last but not least, the limit in your loops is a little off, you're asking for 11 values ;)
(I edited this post, I was wrong about only asking for 9 values. I tend to confuse that sort of stuff)
#include <stdio.h>
int main (void){
int n;
int counter = 0;
printf("How many numbers do you want to enter? \n");
scanf("%d", &n);
int a[n];
printf("OK! now enter your number: \n");
for (int i = 0; i < n; i++){
scanf("%d", &a[i]);
counter += a[i];
}
printf("The answer is: %d\n", counter);
return 0;
}
You are using variable length arrays. At run time the value of n must be known. Place the declaration
int a[n];
after taking input for n, i.e, after scanf("%d", &n); and initialize counter to zero before using it otherwise you will get garbage value (because of undefined behavior).
Also change the for loop condition from i <= n to i < n.
After this line:
int n;
What do you think the value of n is?
Now go to the next line:
int a[n];
How big is this array?
Can you access it properly?