add code comment, update graph cheatsheet

yennanliu · Sep 30, 2023 · 8afc429 · 8afc429
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diff --git a/doc/cheatsheet/graph.md b/doc/cheatsheet/graph.md
@@ -55,6 +55,83 @@
     - longest_path
     - is_cycle
 
+
+#### 1-1-1) Number of Distinct Islands
+    - LC 694
+    ```java
+    // java
+    void dfs(char[][] grid, int r, int c){
+        int nr = grid.length;
+        int nc = grid[0].length;
+
+        if (r < 0 || c < 0 || r >= nr || c >= nc || grid[r][c] == '0') {
+            return;
+        }
+
+        grid[r][c] = '0';
+
+        /** NOTE here !!!*/
+        dfs_1(grid, r - 1, c);
+        dfs_1(grid, r + 1, c);
+        dfs_1(grid, r, c - 1);
+        dfs_1(grid, r, c + 1);
+    }
+
+    public int numIslands_1(char[][] grid) {
+        if (grid == null || grid.length == 0) {
+            return 0;
+        }
+
+        int nr = grid.length;
+        int nc = grid[0].length;
+        int num_islands = 0;
+
+        for (int r = 0; r < nr; ++r) {
+            for (int c = 0; c < nc; ++c) {
+                if (grid[r][c] == '1') {
+                    ++num_islands;
+                    dfs_1(grid, r, c);
+                }
+            }
+        }
+
+        return num_islands;
+    }
+
+    ```
+
+
+#### 1-1-2) Max Area of Island
+    - LC 695
+    ```java
+    // java
+    int[][] grid;
+    boolean[][] seen;
+
+    public int area(int r, int c) {
+        if (r < 0 || r >= grid.length || c < 0 || c >= grid[0].length ||
+                seen[r][c] || grid[r][c] == 0)
+            return 0;
+        seen[r][c] = true;
+        
+        /** NOTE !!!*/
+        return (1 + area(r+1, c) + area(r-1, c)
+                + area(r, c-1) + area(r, c+1));
+    }
+
+    public int maxAreaOfIsland_1(int[][] grid) {
+        this.grid = grid;
+        seen = new boolean[grid.length][grid[0].length];
+        int ans = 0;
+        for (int r = 0; r < grid.length; r++) {
+            for (int c = 0; c < grid[0].length; c++) {
+                ans = Math.max(ans, area(r, c));
+            }
+        }
+        return ans;
+    }
+    ```
+
 ## 2) LC Example
 
 ### 2-1) Closest Leaf in a Binary Tree

diff --git a/leetcode_java/src/main/java/LeetCodeJava/DFS/PathSum.java b/leetcode_java/src/main/java/LeetCodeJava/DFS/PathSum.java
@@ -7,6 +7,7 @@
 
 public class PathSum {
 
+    // V0
     public boolean hasPathSum(TreeNode root, int targetSum) {
 
         if (root == null){