aboutsummaryrefslogtreecommitdiff
path: root/num_closed_islands.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'num_closed_islands.cpp')
-rw-r--r--num_closed_islands.cpp61
1 files changed, 61 insertions, 0 deletions
diff --git a/num_closed_islands.cpp b/num_closed_islands.cpp
new file mode 100644
index 0000000..b6a4a9e
--- /dev/null
+++ b/num_closed_islands.cpp
@@ -0,0 +1,61 @@
+// 1254. Number of Closed Islands
+#include "leetcode.h"
+
+/*
+ * given 2d 'grid' consists of 0's (land) and 1's (water). an island is a
+ * maximal four directionally connected group of 0's and a closed island is an
+ * island totally (all left, top, right, bottom) surrouned by 1's. return the
+ * number of closed islands.
+ */
+
+class Solution {
+ int dx[4] = {0, 0, -1, 1}, dy[4] = {1, -1, 0, 0};
+ bool is_valid(vvd(int) & grid, int i, int j, int r, int c) {
+ if (i >= 0 && i < r && j >= 0 && j < c && grid[i][j] == 0)
+ return true;
+ else
+ return false;
+ }
+ void dfs(vvd(int) & grid, int i, int j, int r, int c) {
+ grid[i][j] = 1;
+ for (int x = 0; x < 4; ++x) {
+ int new_x = i + dx[x];
+ int new_y = i + dy[x];
+ if (is_valid(grid, new_x, new_y, r, c))
+ dfs(grid, new_x, new_y, r, c);
+ }
+ }
+
+public:
+ int closedIsland(vvd(int) & grid) {
+ int r = grid.size(), c = grid[0].size(), ans = 0;
+ for (int i = 0; i < r; ++i)
+ for (int j = 0; j < c; ++j)
+ if (i * j == 0 || i == r - 1 || j == c - 1)
+ if (grid[i][j] == 0)
+ dfs(grid, i, j, r, c);
+ for (int i = 0; i < r; ++i)
+ for (int j = 0; j < c; ++j)
+ if (grid[i][j] == 0) {
+ ans++;
+ dfs(grid, i, j, r, c);
+ }
+ return ans;
+ }
+};
+
+int main() {
+ Solution obj;
+ vvd(int) g1 = {{1, 1, 1, 1, 1, 1, 1, 0},
+ {1, 0, 0, 0, 0, 1, 1, 0},
+ {1, 0, 0, 0, 0, 1, 0, 1},
+ {1, 1, 1, 1, 1, 1, 1, 0}};
+ vvd(int) g2 = {{0, 0, 1, 0, 0}, {0, 1, 0, 1, 0}};
+ vvd(int)
+ g3 = {{1, 1, 1, 1, 1, 1, 1}, {1, 0, 0, 0, 0, 0, 1}, {1, 0, 1, 1, 1, 0, 1},
+ {1, 0, 1, 0, 1, 0, 1}, {1, 0, 1, 1, 1, 0, 1}, {1, 0, 0, 0, 0, 0, 1},
+ {1, 1, 1, 1, 1, 1, 1}};
+ printf("%d\n", obj.closedIsland(g1)); // expect: 2
+ printf("%d\n", obj.closedIsland(g2)); // expect: 1
+ printf("%d\n", obj.closedIsland(g3)); // expect: 2
+}