Created
May 8, 2024 14:51
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number_of_islands.cpp
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| class Solution { | |
| public: | |
| bool flood_fill_nonrecursive(vector<vector<char>>& grid, int px, int py) { | |
| struct frame { | |
| int x, y; | |
| }; | |
| vector<frame> stack; | |
| stack.emplace_back(frame{px,py}); | |
| bool flooded_island = false; | |
| while (!stack.empty()) { | |
| auto [x, y] = stack.back(); | |
| stack.resize(stack.size()-1); | |
| if (x < 0 || x >= grid.size()) { | |
| continue; | |
| } | |
| if (y < 0 || y >= grid[x].size()) { | |
| continue; | |
| } | |
| if (grid[x][y] == '1') { | |
| flooded_island = true; | |
| grid[x][y] = 'x'; | |
| stack.emplace_back(frame{x, y - 1}); | |
| stack.emplace_back(frame{x, y + 1}); | |
| stack.emplace_back(frame{x + 1, y}); | |
| stack.emplace_back(frame{x - 1, y}); | |
| } | |
| } | |
| return flooded_island; | |
| } | |
| void flood_fill(vector<vector<char>>& grid, int x, int y, char c) { | |
| if (x < 0 || x >= grid.size()) { | |
| return; | |
| } | |
| if (y < 0 || y >= grid[x].size()) { | |
| return; | |
| } | |
| if (grid[x][y] == '1') { | |
| if (c == ' ') { | |
| c = next_char(); | |
| } | |
| grid[x][y] = c; | |
| flood_fill(grid, x, y - 1, c); | |
| flood_fill(grid, x, y + 1, c); | |
| flood_fill(grid, x + 1, y, c); | |
| flood_fill(grid, x - 1, y, c); | |
| } | |
| } | |
| int numIslands(vector<vector<char>>& grid) { | |
| int islands = 0; | |
| for (size_t i = 0; i < grid.size(); ++i) { | |
| for (size_t j = 0; j < grid[i].size(); ++j) { | |
| if (grid[i][j] == '1') { | |
| if (flood_fill_nonrecursive(grid, i,j)) { | |
| islands++; | |
| } | |
| } | |
| } | |
| } | |
| return islands; | |
| } | |
| }; |
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