566

class Solution {
public:
    vector<vector<int>> matrixReshape(vector<vector<int>>& mat, int r, int c) {
        int row = mat.size(), col = mat[0].size();
        if(r*c != row*col)
            return mat;

        vector<vector<int>> nmat;
        for(int i=0; i<r; i++){
            vector<int> tmp;
            for(int j=0; j<c; j++){
                int idx = i*c+j;
                tmp.push_back(mat[idx/col][idx%col]);
            }
            nmat.push_back(tmp);
        }
        return nmat;
    }
};