[C++] vector initialization

In C++, a vector can be initialized with:

1. Constructor initialization with no parameters: vector<int> v;. This will create an empty vector with size 0.
2. Constructor initialization with parameters: vector<int> v(n);. This will create a vector of size n and all its elements will be initialized to 0.
3. Constructor initialization with parameters: vector<int> v(n, m);. This will create a vector of size n with all elements initialized to m.
4. Initialize with curly braces: vector<int> v = {1, 2, 3};. This will create a vector of size 3 with elements 1, 2 and 3.
5. Initialize with curly braces: vector<vector<int>> v = { {1, 2}, {3, 4}};. This will create a two-dimensional vector of size 2, where the first row is {1, 2} and the second row is {3, 4}.
6. Initialize with an iterator: vector<int> v(v1.begin(), v1.end());. This will create a vector identical to v1.
7. Two-dimensional array

//cpp
vector<vector<int>> dp(len, vector<int>(len));

Equivalent to

//java
int[][] dp = new int[len][len]