Thread: Array changes values somehow?

I'm working on a HW problem, and for the life of me, i can't figure out why the array I'm using is changing the values of its variables.
I put a lot of double checking to figure out when it's happening in the code, but I don't WHY it's happening. Can anyone shed some light on this?

Code:

#include <stdio.h>

int main() 
{
	double x[4];
	char OP[4];
	double y[4];
	double answer;
	int operation;


	printf("x:  ");
	scanf("%lf %lf %lf %lf %lf", &x[0], &x[1], &x[2], &x[3], &x[4]);
	while (getchar() != '\n');
	printf("2xCHECK: You entered: %.2lf %.2lf %.2lf %.2lf %.2lf\n", x[0], x[1], x[2], x[3], x[4]);

	printf("OP: ");
	scanf("%c %c %c %c %c", &OP[0], &OP[1], &OP[2], &OP[3], &OP[4]);
	while (getchar() != '\n');
	printf("2xCHECK: You entered: %c %c %c %c %c\n", OP[0], OP[1], OP[2], OP[3], OP[4]);
	printf("y:  ");
	scanf("%lf %lf %lf %lf %lf", &y[0], &y[1], &y[2], &y[3], &y[4]);
	while (getchar() != '\n');
	printf("2xCHECK: You entered: %.2lf %.2lf %.2lf %.2lf %.2lf\n", y[0], y[1], y[2], y[3], y[4]);

	printf("\n\nONCEMORE: You entered: %.2lf %.2lf %.2lf %.2lf %.2lf\n", x[0], x[1], x[2], x[3], x[4]);
//problem happens here. WHY??
	
	for(int k=0;k<5;k++)
	{
		if(OP[k]=='+')
		{	
			operation = 1;
		}
		else if (OP[k]=='-')
		{
			operation = 2;
		}
		else if (OP[k] =='*')
		{
			operation = 3;
		}
		else if (OP[k] =='/')
		{
			operation = 4;
		}
		else
		{
			operation = 0;
		}

		printf("%.2lf %c %.2lf = ", x[k], OP[k], y[k]);

		switch(operation)
		{
			case 1:
				answer = x[k] + y[k];
				break;
			case 2:
				answer = x[k] - y[k];
				break;
			case 3:
				answer = x[k] * y[k];
				break;
			case 4:
				answer = x[k] / y[k];
				break;
			default:
				break;
		}

		printf("%.2lf\n", answer);
	
	}
	

 	return 0;
}

The program is supposed to take the first element of X and use the supplied operation, for the purpose of the example...an asterisk for multiplication, and multiply it against the 1st element of Y. It goes on to the second element...etc...

Here's is what I'm putting into the program:
x: 1.8 2.4 3 4.9 5.5
OP: - * + - /
y: 1.5 2 3.66 4.1 5

And here is my exact output:

Code:

x: 1.8 2.4 3 4.9 5.5
2xCHECK: You entered: 1.80 2.40 3.00 4.90 5.50 
OP: - * + - /
2xCHECK: You entered:  - * + - /
y: 1.5 2 3.66 4.1 5
2xCHECK: You entered: 1.50 2.00 3.66 4.10 5.00


ONCEMORE: You entered: 5.00 2.40 3.00 4.90 0.00 
5.00 - 1.50 = 3.50
2.40 * 2.00 = 6.80
3.00 + 3.66 = 6.66
4.90 - 4.1 = 0.08
0.00 / 5.00 = 0.00

So as you can see, the array of X's, for whatever reason, changes it's [0] and [4] elements for NO REASON right before the for loop. It's very frustrating.
Why is this, and how can I fix it?

Right, i thought that might be it, so I added the printf statement to check if it's putting the right values in the array, also I initialize the array with 5 elements, and I'm accessing all the correct ones.
In the beginning of the program, it even recognizes that I've put all the correct values in, with my first double check.

oh! DUH! Wow, ahahaha. I must've been tired when i wrote this last night. I'll go and fix this....hahaha.
Thanks.

Okay, works great now! hahaha.

thanks for catching that, i wasn't even looking there, since I thought the problem was happening somewhere before the for loop. Problem solved!
Strange how it printed out all 5 values in the beginning, though...

Now, clearly, I'm not that good at all this, do you have any tips?

Ah, yes. I would've, but one of the specific instructions for this particular problem was to not use functions, for whatever reason.