int &unionFind(const int &a)
{
if(repr[a] == a)
return repr[a];
return repr[a] = unionFind(repr[a]);
}
inline short int &unionFind(const short int &a)
{
if(repr[a] != a)
repr[a] = unionFind(repr[a]);
return repr[a];
}
bool unionUnion(const int &a, const int &b)
{
int &fa = unionFind(a),
&fb = unionFind(b);
if(fa == fb)
return false;
if(fa < fb)
repr[fb] = fa;
else
repr[fa] = fb;
return true;
}
int numIslands(vector<vector<char>> &grid) {
if (grid.empty())
return 0;
int count = 0, R = grid.size(), C = grid[0].size();
for (int row = 0; row < R; ++row) {
for (int column = 0; column < C; ++column) {
if (grid[row][column] == '1') {
unionFind(grid, row, column, R, C);
++count;
}
}
}
return count;
}