数组中的向量

Question

如果我有一个向量数组，由于数组的连续存储特性，向量的大小调整能力是否受到限制？

Answer 1

Yes, but not in the way you're thinking.

Vectors have to find contiguous address space for their content. Memory fragmentation may cause the largest contiguous block to be smaller than total free memory. And having many vectors makes fragmentation more likely.

Answer 2

No; internally, vectors hold pointers to the memory blocks, not the block themselves.

Answer 3

resize won't affect the array's memory at all. The vectors have a pointer to the actual storage, so resizing affects some other memory that has nothing to do with the array's. All that will be in the array is basically just pointers pointing to possibly different lengths of memory blocks.

Furthermore, if you have something like this:

std::vector<int> arr [5];

The array's memory will be on the stack, and the vectors' memory will be on the heap. Totally different!