in my first year University class we have just started fiddling with arrays and on the worksheet I was given this code, which doesn't seem to work. I've been scanning and looking for a problem but nothing seems to fix it. Here is my code...
#include <stdio.h>
#include <stdbool.h>
int main(){
int size = 10;
float suspect[size]; //Declaring suspect array
int sizeR = 3;
int sizeC = 10;
float criminals[sizeR][sizeC]; //Declaring criminals array
//Read 10 input values into suspect array from keyboard
printf("Enter the 10 chromosomes of the suspect separated by spaces: \n");
for (int i = 0; i < size; i++)
scanf(" %f", &suspect[i]);
//Read multiple profiles of 10 values into criminals array from the keyboard
for (int i = 0; i < sizeR; i++){
printf("Enter the 10 chromosomes of the %dth criminal: \n", i+1);
//Read 10 input values of a criminal into criminals array from the keyboard
for (int j = 0; j < sizeC; j++)
scanf(" %f", &criminals[i][j]);
}
//Match two profiles
bool match = true;
for (int i = 0; i < size; i++)
if(suspect[i] != criminals[i]) //Error is in this line
match = false;
//Display matching result
if (match)
printf("The two profiles match! \n");
else
printf("The two profiles don't match! \n");
return 0;
}
And when I run this code, I am returned with:
error: invalid operands to binary expression ('float' and 'float [sizeC]')
With the error being pointed to the != in the matching two profiles part. Excuse me if the solution is simple, coding is relatively new to me and I am struggling to find the solution to this particular problem using Google.
In this if statement
if(suspect[i] != criminals[i]) //Error is in this line
the expression criminals[i] is implicitly converted to the type float * because the original type of the expression before the conversion is float[sizeC].
And moreover the expressions suspect[i] has the type float. That is there are compared an object of the type float with a pointer of the type float * that does not make a sense.
So the compiler issues the error message.
If you are going to compare the array suspect with elements of the two-dimensional array criminals you should use one more inner for loop.
Related
I am trying to subtract a given number from an array and then store the results in a completely different array. Is it possible to write the code without using pointers?
I am trying to write the code with using for loop and or do/while loop.
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main(){
int num[100];
int i ;
int size;
int sub;
int diff[100];
printf("Enter the size of the array: ");
scanf("%d", &size);
for(i=0;i<size; i++){
printf("Enter the element %d :", i+1);
scanf("%d", &num[i]);
}
printf(" Enter the number to substract: \n");
scanf("%d", &sub);
for (i=0;i<size; i++)
{
y = num[i]- sub;
scanf("%d", &diff[y]);
}
for (y=0; y<size; y++)
{
printf("%d", diff[y]);
}
}
After I scan the results, I tried different ways to initialize and store the values in the second array but haven't been successful. What mistake am I making here?
y = num[i] - sub;
This is fine, as it's the result of subtraction for a given source array element.
scanf("%d", &diff[y]);
This doesn't make sense, as it's attempting to read input from the user. Not only that, it's using the result of the subtraction as the index of the destination array.
Just assign the result of the subtraction to the corresponding destination array member:
diff[i] = num[i] - sub;
In your question, you try to scan the value to another array, but the correct form is to assign the value in the new array position.
For example, in your first for loop use the i variable as the position and assign num[i] - sub on diff[i]:
for (i = 0; i < size; i++)
{
diff[i] = num[i] - sub;
}
instead of:
for (i=0;i<size; i++)
{
y = num[i]- sub;
scanf("%d", &diff[y]);
}
I was writing a C program to find inversions in an array. The program compiles smoothly but as soon as I run it, it displays a garbage value where I take the array as a input. The program is given below:
#include <stdio.h>
#include <stdlib.h>
int checkInversions(int arr[], int n) {
int i, j, inverse_count = 0;
for (i = 0; i < n - 1; i++) {
for (j = i + 1; j < n; j++) {
if (arr[i] > arr[j]) {
inverse_count++;
}
}
}
return inverse_count;
}
int main() {
int arr[10], i, n;
printf("Enter the elements of the array: %d");
for (i = 0; i <= 10; i++) {
scanf("%d", &arr[i]);
}
n = sizeof(arr) / sizeof(arr[0]);
printf("\n The inverse is: %d", checkInversions(arr, n));
return 0;
}
Now, when the statement Enter the elements of the array: is displayed, just beside that is a garbage value like 623089. I am able to take the input but the result is not correct. What is the cause of this? Any help in this regard will be appreciated.
You are calling printf with a format specifier for %d and nothing passed to satisfy the variable expected by the format string. This is undefined behavior.
What you meant to do was merely:
printf("Enter the elements of the array: ");
Also, since arr has 10 elements, you iterate through it as such:
for(i = 0; i < 10; i++)
You don't need to use sizeof to determine the size of the array since you already know it; it's 10.
I think you are missing the variable that should populate the %d on the printf.
Try taking out the %d on the printf call so it ends up like:
printf("Enter the elements of the array: ");
Or assign the corresponding variable to display with that "%d", like this:
printf("Enter the elements of the array: %d", variable);
Check if that helps!
Your problem is printf("Enter the elements of the array: %d");. You tell the program that you want to print an integer, but you do not specify which integer that is. Remove the %d and the garbage value will be gone, like this: printf("Enter the elements of the array: ");
While I was learning to code in C about structure and pointers, I tried to make a program that calculate grades of students.
I thought it would work from my previous experiences for such calculation without pointers and structure. But with those, it gave me wild results in the program.
#include <stdio.h>
#include <string.h>
/*
The program will scan year, name, score of three different subjects,
and calculate the sum and the average.
Three different people (using array) will be taken into account.
*/
struct grade {
int year;
char name[20];
int score[3];
int total;
float avg;
};
void main() {
struct grade p[3];
char str = 'c';
char *pstr = NULL;
int i, j;
pstr = &str;
for (j = 0; j < 3; j++) {
printf("Year of Admission: ");
scanf("%d", &p[j].year);
printf("Name of the Student: ");
scanf("%s", pstr);
strcpy(p[j].name, pstr);
for (i = 0; i < 3; i++) {
printf("The score for Subject %d: ", i + 1);
scanf("%d", &p[j].score[i]);
p[j].total += p[j].score[i];
}
p[j].avg = p[j].total / 3.0;
}
for (j = 0; j < 3; j++) {
printf("%s's\n", p[j].name);
printf("Total score: %d\n", p[j].total);
printf("Average: %.2f\n", p[j].avg);
}
}
I could have written each of three different subjects as one variable but for an extra "challenge", I made an array inside the structure.
int score[3];
However, the program only prints out extremely small number -89541694... for both totals and averages.
I assume that this particular line inside a for-loop is a problem.
scanf("%d", &p[j].score[i]);
But I could not figure out why. I am really new to pointers and still learning them.
I hope for your generous teaching and explanations.
Thank you in advance.
Local variables are not initialized with 0, so you just need to zero it before calculating total:
p[j].total = 0;
before
for (i = 0; i < 3; i++) {
printf("The score for Subject %d: ", i + 1);
scanf("%d", &p[j].score[i]);
p[j].total += p[j].score[i];
}
The variable pstr points to a single char. A string in C needs to be at least two characters for a single-character string: The actual character, and the null terminator.
When you use e.g. scanf to read a string, the function will write at least two bytes to the memory pointed to by pstr. But since it only points to a single byte you will write out of bounds and that leads to undefined behavior.
If you want to be able to read more than a single character you need to have more space allocated for the string. And you need to limit scanf so it will not write out of bounds.
For example
char pstr[40]; // Allows for strings up to 39 character, plus terminator
// ...
scanf("%39s", pstr); // Read at most 39 characters from standard input, and write to pstr
Another problem is that local variables are not automatically initialized, their values will be indeterminate.
That means the contents of the array p is unknown and seemingly random.
When you do
p[j].total += p[j].score[i];
you use the seemingly random value of p[j].total to calculate another seemingly random number.
To initialize all structures and all their members to "zero" in the array, do e.g.
struct grad p[3] = { 0 };
Instead of making pstr a pointer you might wanted to do somehting like this
char pstr[30];
And accordingly you will scanf the string using scanf("%29s",pstr); and check it's return value.
To describe the problem a bit - you had a pointer pointing to a char which is not capable of holding an input characters and the corresponding \0 (nul terminating character). As a result this gives rise to undefined behavior. And then using it in strcpy is also an illegal code. (Undefined behavior).
Here the solution I gave simply declared an array of 30 characters and we limited the string input using scanf upto 29 characters because we need to store the terminating null.
Showing you atleast a bit of code to make you understand how to write these codes:-
if( scanf("%29s",pstr)!= 1){
fprintf(stderrm"Error in input");
exit(EXIT_FAILURE);
}
Another problem is initialize the variables - here you used p[j].total += p[j].score[i]; What is the value of p[j].total initially. It contains garbage value. In the loop make p[j].total = 0; first. That will give you the correct result.
Note: The wild results are the garbage value resulted from addition of some garbage value with p[j].score[i].
Also note that without making the changes that I said if you only change the initialization thing then also code is not guranteed to work. undefined behavior is undefined behavior - cases may arise which will simply crash the program making you wonder where you went wrong.
Illustration code may help you:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
/*
The program will scan year, name, score of three different subjects,
and calculate the sum and the average.
Three different people (using array) will be taken into account.
*/
struct grade {
int year;
char name[20];
int score[3];
int total;
float avg;
};
int main(void) {
struct grade p[3];
char pstr[20];
int i, j;
for (j = 0; j < 3; j++) {
printf("Year of Admission: ");
if(scanf("%d", &p[j].year)!=1){
fprintf(stderr, "%s\n", "Error in input");
exit(EXIT_FAILURE);
}
printf("Name of the Student: ");
if(scanf("%19s", pstr)!=1){
fprintf(stderr, "%s\n", "Error in input");
exit(EXIT_FAILURE);
}
strcpy(p[j].name, pstr);
p[j].total = 0;
for (i = 0; i < 3; i++) {
printf("The score for Subject %d: ", i + 1);
if(scanf("%d", &p[j].score[i])!=1){
fprintf(stderr, "%s\n", "Error in input");
exit(EXIT_FAILURE);
}
if(p[j].score < 0){
fprintf(stderr, "%s\n", "Error in input");
exit(EXIT_FAILURE);
}
p[j].total += p[j].score[i];
}
p[j].avg = p[j].total / 3.0;
}
for (j = 0; j < 3; j++) {
printf("%s's\n", p[j].name);
printf("Total score: %d\n", p[j].total);
printf("Average: %.2f\n", p[j].avg);
}
return 0;
}
In fact instead of using the pstr just input the names directly in the structure variable instance itself. No need to use a temporary variable.
So I'm trying to solve this http://www.codeabbey.com/index/task_view/sum-in-loop and I have 45 random numbers to input. I'm coding using C so I want to use the scanf function. The problem is that since it's 45 numbers (which are separated by spaces) what I want to do is copy paste the values so that the program can solve them from an array. Should I do it like this:
int x [45];
scanf("%d %d....(x42) %d",&x,&x,...(x42),&x);
or is there a more efficient way of doing this? (I hope there is T_T)
You need not (and you should not) write a single format string containing 45(or whatever) format specifier, following 45 pointers.
You need to use a loop.
Example:
for loop with an array, will hold the supplied operands, too
int x[45] = {0};
int sum = 0;
for (int i = 0; i < 45; i++) //style supported over C99
{
scanf("%d", &x[i]);
sum += x[i];
}
printf("sum = %d\n", sum);
for loop without an array, won't hold the operands, only result
int x = 0;
int sum = 0;
for (int i = 0; i < 45; i++) //style supported over C99
{
scanf("%d", &x);
sum += x;
}
printf("sum = %d\n", sum);
I have a class project to make an array, declare it's size (add 1) then fill it in numerical, nondecreasing order. After that, I need to declare x, a value to be added to the array in the appropriate spot, so the array is still nondecreasing.
The program builds without error (for once!) but I'm getting some really weird outputs.
#include <stdio.h>
int main (void) {
//Local Declarations
int size;
int ary[100];
int x;
int i;
int j;
//Statements
printf("Enter the size of the array: ");
scanf("%d", &size);
printf("\nEnter digits to fill the array, in numerical order: ");
for (i = 0; i < size; i++) scanf("%d", &ary[i]);
size++;
printf("\nInput x, the value to add to the array: ");
scanf("%d", &x);
while(i <= x && x > ary[i]){
i++;
j = size - 1;
while(j >= i) {
ary[j++] = ary[j];
j--;
}
}
for(i = 1; i < size; i++) {
printf("%d", &ary[i]);
}
return 0;
} //main
When it runs I get:
Enter the size of the array: 3
Enter digits to fill the array, in numerical order: 1
2
3
Input x, the value to add to the array: 4
268634426863482686352
Process returned 0 (0x0) execution time : 7.124 s
Press any key to continue.
I would examine your print function . It looks like you're printing the memory address of that particular array index rather than the value at that spot in the array.
Don't increase the size variable before you iterate through. Then walk backwards through the array, and populate as needed.
for (i = size; i >0; --i)
{
if (ary[i-1] > x)
{
ary[i] = ary[i-1];
}
else
{
ary[i] = x;
break;
}
}
if (i == 0)
ary[i] = x;
Afterwards, you can increase size as you print the output.
I've reproduced your desired output using this array walk.
There are other ways that I would solve this problem in real life, but this works well enough within your existing code.
First things first: what do you EXPECT to see as the output?
Second things first: you aren't clearing out the memory for the array before use. You have garbage values in any slots you aren't using.
Third things first: using GCC I'm seeing at least two warnings without even trying.
test.c:32:15: warning: format specifies type 'int' but the argument has type 'int *' [-Wformat]
printf("%d", &ary[i]);
test.c:27:14: warning: unsequenced modification and access to 'j' [-Wunsequenced]
ary[j++] = ary[j];
In your printing loop your are not printing the value but your are printing the address of that element. Change the last loop to
for(i = 1; i < size; i++) {
printf("%d", ary[i]);
}
I am not sure why your are printing the array from index 1. But if you want to print whole array you should initialize i to zero in above loop.