For problem: D1. Dances (Easy version)

My approach: I sorted both arrays in increasing order. Then, using two pointers i and j for arrays b and a respectively, initially pointing to the last element. I move both pointers to the left in the case where a[j] < b[i]. Otherwise, I use a while loop to find the first element to the left of pointer j that is less than b[i], adding the count of the number of elements of a I skipped.

Initially, I forgot to put a check on the value of j in case it becomes less than 0, which could result in a runtime error as I will try to access an element out of the bound. Surprisingly, it got accepted when calling the function by passing copy of the vector, and the same code resulted in a runtime error when called by passing the vector as a reference.

Here are my submissions:

Submission 1 passing vector as reference without check on j. Runtime error because j can become < 0 and I will try to access an undefined address.

Submission 2 passing copy of vector without check on j. Accepted. Why it's not giving runtime error similar to Submission 1.

Submission 3 passing vector as reference with check on j. Accepted.

Can you help me understand why Submission 2 got accepted even though it should give runtime error similar to Submission 1.

Thank you.