add solution of number-of-islands

Author: jinhyungrhee

number-of-islands/jinhyungrhee.java

@@ -0,0 +1,33 @@
+class Solution {
+
+    public int numIslands(char[][] grid) {
+
+        int[][] dir = {{-1, 0}, {1, 0}, {0, 1}, {0, -1}};
+        boolean[][] visited = new boolean[grid.length][grid[0].length];
+
+        int count = 0;
+        for (int i = 0; i < grid.length; i++) {
+            for (int j = 0; j < grid[0].length; j++) {
+                if ('1' == grid[i][j] && !visited[i][j]) {
+                    dfs(grid, visited, dir , i, j);
+                    count++;
+                }
+            }
+        }
+        return count;
+    }
+
+    public void dfs(char[][] grid, boolean[][] visited, int[][] dir, int x, int y) {
+
+        if (x >= 0 && x < grid.length && y >= 0 && y < grid[0].length
+                && !visited[x][y] && '1' == grid[x][y]) {
+
+            visited[x][y] = true;
+            for (int i = 0; i < 4; i++) {
+                int dx = x + dir[i][0];
+                int dy = y + dir[i][1];
+                dfs(grid, visited, dir ,dx, dy);
+            }
+        }
+    }
+}