Max Area of Island
DFS
- loop through grid and store pair of
i, jin set, wheregrid[i][j] == 1. - do DFS, where everytime traverse a vaild value, remove it from the set, as well as grid.
cpp
set<pair<int,int>>st;
int maxAreaOfIsland(vector<vector<int>>& grid) {
int res = 0;
for(int i = 0; i < grid.size(); i++)
for(int j = 0; j < grid[0].size(); j++)
if(grid[i][j] == 1)
st.insert({i,j});
while(!st.empty()){
auto it = st.begin();
int a = dfs(grid, it->first, it->second);
res = max(res, a);
}
return res;
}
int dfs(vector<vector<int>>& grid, int i, int j) {
if(i >= grid.size() || j >= grid[0].size() || grid[i][j] == 0)
return 0;
grid[i][j] = 0;
st.erase({i,j});
int re = 0;
re = 1 + dfs(grid, i+1, j) + dfs(grid, i, j+1) + dfs(grid, i-1, j) + dfs(grid, i, j-1);
return re;
}