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Diffstat (limited to 'other/min_num_days_disconnect_island.cpp')
-rw-r--r-- | other/min_num_days_disconnect_island.cpp | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/other/min_num_days_disconnect_island.cpp b/other/min_num_days_disconnect_island.cpp new file mode 100644 index 0000000..ff54c44 --- /dev/null +++ b/other/min_num_days_disconnect_island.cpp @@ -0,0 +1,62 @@ +// 1568. Minimum Number of Days to Disconnect Island +#include "leetcode.h" + +/* + * you are given an 'm * n' binary grid where 1 represents land and 0 represents + * water. an island is a maximal 4 directionally horizontal or vertical + * connected group of 1's. the grid is said to be connected if we have exactly + * one island otherwise it is disconnected. in one day, we are allowed to change + * any single land cell 1 into a water cell 0. return the minimum number of days + * to disconnect the grid. + */ + +class Solution { +public: + int minDays(vector<vector<int>> &grid) { + int islands = cnt_islands(grid), n = grid.size(), m = grid[0].size(); + if (islands > 1 || !islands) + return 0; + else + for (int i = 0; i < n; i++) + for (int j = 0; j < m; j++) + if (grid[i][j]) { + grid[i][j] = 0; + islands = cnt_islands(grid); + grid[i][j] = 1; + if (islands > 1 || !islands) + return 1; + } + return 2; + } + +private: + vector<int> dx = {1, -1, 0, 0}, dy = {0, 0, 1, -1}; + void dfs(int x, int y, vector<vector<int>> &grid, vector<vector<int>> &vis) { + int n = grid.size(), m = grid[0].size(); + vis[x][y] = 1; + for (int i = 0; i < 4; i++) { + int nx = x + dx[i], ny = y + dy[i]; + if (nx >= 0 and ny >= 0 and nx < n and ny < m and !vis[nx][ny] and + grid[nx][ny]) + dfs(nx, ny, grid, vis); + } + } + int cnt_islands(vector<vector<int>> &grid) { + int res = 0, n = grid.size(), m = grid[0].size(); + vector<vector<int>> vis(n, vector<int>(m, 0)); + for (int i = 0; i < n; i++) + for (int j = 0; j < m; j++) + if (!vis[i][j] && grid[i][j]) { + dfs(i, j, grid, vis); + res++; + } + return res; + } +}; + +int main() { + Solution obj; + vvd g1 = {{0, 1, 1, 0}, {0, 1, 1, 0}, {0, 0, 0, 0}}, g2 = {{1, 1}}; + printf("%d\n", obj.minDays(g1)); // expect: 2 + printf("%d\n", obj.minDays(g2)); // expect: 2 +} |