vector<int>G[] 和 vector<vector<int> G 的区别

来自：http://stackoverflow.com/questions/28712364/difference-between-vector-int-v-and-vector-vectorint-v

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1. Using arrays are C-style coding, using vectors are C++-style coding.

Vectors are sequence containers representing arrays that can change in size.

Just like arrays, vectors use contiguous storage locations for their elements, which means that their elements can also be accessed using offsets on regular pointers to its elements, and just
as efficiently as in arrays. But unlike arrays, their size can change dynamically, with their storage being handled automatically by the container.

When you want to work with a fixed number of 

std::vector

 elements,
you can use 

vector
<int> V[]

.

When you want to work with a dynamic array of 

std::vector

,
you can use 

vector<
vector<int> > V

.

2.

One difference would be that although both can be initialized in the same way, e.g. vector<int> V1[] {{1,2,3}, {4,5,6}}; vector<vector<int>> V2 {{1,2,3}, {4,5,6}}; and accessed cout << V1[0].back() << endl; cout << V2[0].back() << endl; the V1 can't grow. You cannot make V1.push_back(...) as its not a vector object. Its just an array. Second one is dynamic. You can grow it as you please

11down vote

One difference would be that although both can be initialized in the same way, e.g. vector<int> V1[] {{1,2,3}, {4,5,6}}; vector<vector<int>> V2 {{1,2,3}, {4,5,6}}; and accessed cout << V1[0].back() << endl; cout << V2[0].back() << endl; the V1 can't grow. You cannot make V1.push_back(...) as its not a vector object. Its just an array. Second one is dynamic. You can grow it as you please