Java (Need Help)

Question

https://code.sololearn.com/cvirEMwQI2VO/?ref=app

While I was doing the java play/challenge I stumbled across this question and I was wondering if anyone can explain how did it get 51 as the answer? I tried slowly debugging and understand but I just couldn't.... Any help would be appreciated

Answer 1

It's a 2D-Array stored as a 1D array :)
If you look at that double loop, every 100 iterations will make y bigger by 1, and x resets.

So at 99, y = 0, x = 99
At 100, y = 1, x = 0
And at 150, y = 1, x = 50

And pixels[i] is set to x+y of course so 1 + 50 = 51.

Theres actually a formula for that:

To figure out x and y given i:

x = i % width
y = i / width

Answer 2

//for y=0 , index can't be greater than 100 obviously , for y=1 & x = 50 , index will be 150

// for index 150 , x+y = 50+1 therefore answer is 51

//hope it helps ☺

Answer 3

So we are going to find pixels[150].

We know that from the loop:-

index = x + y * 100;
pixels[index] = x + y;

Plug in 150 and we will get:-

150 = x + y * 100;
pixels[150] = x + y

and since the value of x and y falls between 0 and 99 inclusive, then it must be:-

x = 50
y = 1
*which satisfy 150 = 50 + 1 * 100

Therefore, pixels[150] = x + y = 50 + 1 = 51.

Answer 4

Thank you everyone I figured out why I couldn't find the answer in the beginning..... I totally forgot about simple BODMAS where I need to multiply first before I add.... Which is why I couldn't get the answer.

Thank you everyone for answering to my help :)