no match for 'operator=' in vector[][]

[redmonkey]

#include <iostream>
#include <math.h>
#include <vector>
using namespace std;

int main (void) {

int sv = 0, fv = 0;

cout << "Start Value:" << endl;
cin >> sv;
cout << "End Value:" << endl;
cin >> fv;
cout << endl;

int size = (int)sqrt(fv-sv)+5;

vector <vector<int> > grid [size][size];
vector <vector<int> > grid2 [15][15];

int midx = (int)(sqrt(fv-sv)+5/2)-1, midy = (int)(sqrt(fv-sv)+5/2)-1;
int down = 0, right = 0, left = 0, up = 0;
int yy = 0, xx = 0;
int count = 0;
string dir = "down";

for (int i = 0; i <= 5 ; i++) {

if (dir=="down") {
for (int i2 = 0; i2 < 1 ; i2++) {
grid2[1][1] = 5;
grid[0][0] = 5;
grid [midx][midy] = i;
}
dir = "right";
}

}






}

When I compile the code above, I get this error "no match for 'operator=' in 'grid2[1][1] = 5' ". I'm clueless as to what's the problem... Thx!


31 C:\Documents and Settings\Administrator\Desktop\Testing Files Folder\J42001.cpp no match for 'operator=' in 'grid2[1][1] = 5'

note C:\Dev-Cpp\include\c++\3.4.2\bits\vector.tcc:131 candidates are: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>:perator=(const std::vector<_Tp, _Alloc>&) [with _Tp = std::vector<int, std::allocator<int> >, _Alloc = std::allocator<std::vector<int, std::allocator<int> > >]

32 C:\Documents and Settings\Administrator\Desktop\Testing Files Folder\J42001.cpp no match for 'operator=' in 'grid[0][0] = 5'

[Daved]

You're using the wrong syntax for construction. To construct grid2 with an initial size of 15x15 use this syntax:

vector <vector<int> > grid2(15, vector<int>(15));

That will create 15 vectors each containing 15 integers initialized to 0. You'll have to do something similar for the grid variable.

[redmonkey]

ohmygods. Thank you !

[cpjust]

If you don't need the vector to grow then why not just use a plain old array?
Otherwise use the push_back() member function to add elements to the vector.

[Elysia]

Better yet, std::tr1::array or boost::array.

[Daved]

>> If you don't need the vector to grow then why not just use a plain old array?

That won't work for grid, since it has a dynamic size. Might as well use vector for both and initialize the size in the constructor since you can determine that size when you create the instance.