int numIslands(vector<vector<char>>& grid) {
int m = grid.size();
if (m == 0) return 0;
int n = grid[0].size();
if (n == 0) return 0;
make_set(id, m , n);
num_components = (grid[0][0] == '1');
// i == 0
for (int j = 1; j < n; j++) {
if (grid[0][j] == '0') continue;
num_components++;
if (grid[0][j - 1] == '1')
unions(to1d(0, j, n), to1d(0, j - 1, n));
}
// j == 0
for (int i = 1; i < m; i++) {
if (grid[i][0] == '0') continue;
num_components++;
if (grid[i - 1][0] == '1')
unions(to1d(i, 0, n), to1d(i - 1, 0, n));
}
//i != 0 && j != 0
for (int i = 1; i < m; i++) {
for (int j = 1; j < n; j++) {
if (grid[i][j] == '0') continue;
num_components++;
if (grid[i - 1][j] =='1') {
unions(to1d(i, j, n), to1d(i - 1, j, n));
}
if (grid[i][j - 1] == '1') {
unions(to1d(i, j, n), to1d(i, j - 1, n));
}
}
}
return num_components;
}
std::vector<int> const &
createSumTable(float const *volume, Vec3 extents, std::function<int(float)> empty)
{
svt::extents = extents;
svt::sumTable.resize(size_t(extents.x) * size_t(extents.y) * size_t(extents.z));
for(int z = 1; z < extents.z; ++z) {
for(int y = 1; y < extents.y; ++y) {
for(int x = 1; x < extents.x; ++x) {
size_t idx{ to1d(x, y, z, extents.x, extents.y) };
int v1{ empty(volume[idx]) };
int v2{ v1 + get_check(x, y, z - 1)
+ (get_check(x - 1, y, z) - get_check(x - 1, y, z - 1))
+ (get_check(x, y - 1, z) - get_check(x, y - 1, z - 1))
- (get_check(x - 1, y - 1, z) - get_check(x - 1, y - 1, z - 1))
};
svt::sumTable[idx] = v2;
}}}
return svt::sumTable;
}
