Mixing up delete and delete[]

Explain the difference between delete and delete[] in C++, and what happens if you use the wrong one.

delete frees one object from new; delete[] frees an array from new[], calling every element's destructor. Mismatching them is undefined behaviour: typically only the first destructor runs, or the allocator is handed the wrong address, corrupting the heap or crashing. Prefer std::vector and smart pointers so you never write either.