Number Of Islands

Author: TonyKim9401

number-of-islands/TonyKim9401.java

@@ -0,0 +1,28 @@
+// TC: O(n * m)
+// retrieve all elemetns, grid.length * grid[0].length
+// SC: O(n * m(
+// need to change all elements from 1 to 0 in the worst case
+class Solution {
+    int output = 0;
+    public int numIslands(char[][] grid) {
+        for (int i = 0; i < grid.length; i++) {
+            for (int j = 0; j < grid[0].length; j++) {
+                if (grid[i][j] == '1') {
+                    output += 1;
+                    countIslands(i, j, grid);
+                }
+            }
+        }
+        return output;
+    }
+
+    private void countIslands(int i, int j, char[][] grid) {
+        if (i < 0 || i >= grid.length || j < 0 || j >= grid[0].length) return;
+        if (grid[i][j] == '0') return;
+        grid[i][j] = '0';
+        countIslands(i+1, j, grid);
+        countIslands(i-1, j, grid);
+        countIslands(i, j+1, grid);
+        countIslands(i, j-1, grid);
+    }
+}