2024/9/3 Hot100 graph

src/main/java/com/cool/hot100/graph/Num200.java

@@ -0,0 +1,45 @@
+package com.cool.hot100.graph;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/03/11:24
+ * DayNumber 2
+ * Hard 2
+ * Level ?
+ */
+
+public class Num200 {
+
+    public int numIslands(char[][] grid) {
+        int res = 0;
+        for (int i = 0; i < grid.length; i++) {
+            for (int j = 0; j < grid[i].length; j++) {
+                if (grid[i][j] == '1') {
+                    res++;
+                    dfs(grid, i, j);
+                }
+            }
+        }
+        return res;
+    }
+
+    private void dfs(char[][] grid, int x, int y) {
+        if (!isInArea(grid, x, y)) {
+            return;
+        }
+        if (grid[x][y] != '1') {
+            return;
+        }
+        grid[x][y] = '2';
+        dfs(grid, x + 1, y);
+        dfs(grid, x, y + 1);
+        dfs(grid, x, y - 1);
+        dfs(grid, x - 1, y);
+    }
+
+    private boolean isInArea(char[][] grid, int x, int y) {
+        return x >= 0 && y >= 0 && x < grid.length && y < grid[0].length;
+    }
+}