Pond Sizes：统计一片矩形区域中连通的池塘数目。
只需要遍历每一个点，深搜统计连通的池塘大小，最后排序返回即可。
class Solution { public: vector<int> pondSizes(vector<vector<int>>& land) { vector<int> sizes; Visited.assign(land.size(), vector<bool>(land[0].size(), false)); for(size_t r = 0; r < land.size(); r++) { for(size_t c = 0; c < land[r].size(); c++) { if(land[r][c] == 0 && !Visited[r][c]){ int size = ComputeSize(land, static_cast<int>(r), static_cast<int>(c)); sizes.push_back(size); } } } sort(sizes.begin(), sizes.end()); return sizes; } private: vector<vector<bool>> Visited; int ComputeSize(const vector<vector<int>> &land, const int r, const int c) { if(r < 0 || r >= land.size() || c < 0 || c >= land[r].size()) return 0; if(land[r][c] != 0 || Visited[r][c]) return 0; int size = 1; Visited[r][c] = true; for(int dr = -1; dr <= 1; dr++) { for(int dc = -1; dc <= 1; dc++) { size += ComputeSize(land, r + dr, c + dc); } } return size; } };