void expandFrom(int i, int j, std::vector<std::vector<char>>& grid)
{
if (i - 1 >= 0)
{
if (grid[i - 1][j] == '1' && !copy[i - 1][j])
{
copy[i - 1][j] = copy[i][j];
expandFrom(i - 1, j, grid);
}
}
if (j - 1 >= 0)
{
if (grid[i][j - 1] == '1' && !copy[i][j - 1])
{
copy[i][j - 1] = copy[i][j];
expandFrom(i, j - 1, grid);
}
}
if (i + 1<h)
{
if (grid[i + 1][j] == '1' && !copy[i + 1][j])
{
copy[i + 1][j] = copy[i][j];
expandFrom(i + 1, j, grid);
}
}
if (j + 1<w)
{
if (grid[i][j + 1] == '1' && !copy[i][j + 1])
{
copy[i][j + 1] = copy[i][j];
expandFrom(i, j + 1, grid);
}
}
}
string longestPalindrome(string s) {
if (s.size() <= 1) return s;
int n = s.size();
string longest = s.substr(0, 1);
for (int i = 0; i < n; ++i)
{
string p = expandFrom(s, i, i);
string q = expandFrom(s, i, i+1);
if (p.size() > longest.size())
longest = p;
if (q.size() > longest.size())
longest = q;
}
return longest;
}
int numIslands(std::vector<std::vector<char>>& grid) {
h = grid.size();
if (h == 0)
return 0;
w = grid[0].size();
for (int i = 0; i<h; ++i)
{
copy.push_back(std::vector<bool>());
for (int j = 0; j<w; ++j)
copy[i].push_back(false);
}
int num_islands = 0;
for (int i = 0; i<h; ++i)
{
for (int j = 0; j<w; ++j)
{
if (grid[i][j] == '1' && !copy[i][j])
{
++num_islands;
copy[i][j] = true;
expandFrom(i, j, grid);
}
}
}
return num_islands;
}