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| class Solution {
vector<vector<int>> visited;
public:
int numIslands(vector<vector<char>>& grid) {
if(grid.empty()) return 0;
if(grid[0].empty()) return 0;
int islandNum = 0;
visited = vector<vector<int>>(grid.size(), vector<int>(grid[0].size(), false));
for(int i = 0; i < grid.size(); i++){
for(int j = 0; j < grid[0].size(); j++){
if(grid[i][j] == '1' && !visited[i][j]) {
BFS(grid, i, j);
++islandNum;
}
}
}
return islandNum;
}
void BFS(vector<vector<char>> &g, int x, int y){
visited[x][y] = true;
g[x][y] = '0';
queue<pair<int, int>> BFS;
BFS.push(pair<int, int>(x, y));
while(!BFS.empty()){
pair<int, int> pos = BFS.front();
int curX = pos.first, curY = pos.second;
if(curX - 1 >= 0 && g[curX - 1][curY] == '1' && !visited[curX - 1][curY]){
BFS.push(pair<int, int>(curX - 1, curY));
visited[curX - 1][curY] = true;
}
if(curX + 1 < g.size() && g[curX + 1][curY] == '1' && !visited[curX + 1][curY]){
BFS.push(pair<int, int>(curX + 1, curY));
visited[curX + 1][curY] = true;
}
if(curY - 1 >= 0 && g[curX][curY - 1] == '1' && !visited[curX][curY - 1]){
BFS.push(pair<int, int>(curX, curY - 1));
visited[curX][curY - 1] = true;
}
if(curY + 1 < g[0].size() && g[curX][curY + 1] == '1' && !visited[curX][curY + 1]){
BFS.push(pair<int, int>(curX, curY + 1));
visited[curX][curY + 1] = true;
}
BFS.pop();
}
}
};
|