fd

Author: dingjikerbo

README.md

@@ -373,6 +373,7 @@
 |538|[Convert BST to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/)|[Java](leetcode/solution/src/ConvertBSTToGreaterTree.java)|100||
 |541|[Reverse String II](https://leetcode.com/problems/reverse-string-ii/)| [Java](leetcode/solution/src/ReverseStringII.java)|100||
 |543|[Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/)|[Java](leetcode/solution/src/DiameterOfBinaryTree.java)|80|这题易错|
+|547|[Friend Circles](https://leetcode.com/problems/friend-circles/)|[Java](leetcode/solution/src/FriendCircles.java)|70||
 |557|[Reverse Words in a String III](https://leetcode.com/problems/reverse-words-in-a-string-iii/)| [Java](leetcode/solution/src/ReverseWordsInAStringIII.java)|100||
 |560|[Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k/)| [Java](leetcode/solution/src/SubarraySumEqualsK.java)|70||
 |606|[Construct String from Binary Tree](https://leetcode.com/problems/construct-string-from-binary-tree/)|[Java](leetcode/solution/src/ConstructStringFromBinaryTree.java)|90||

leetcode/solution/src/FriendCircles.java

@@ -0,0 +1,26 @@
+public class FriendCircles {
+
+    public int findCircleNum(int[][] M) {
+        int num = 0;
+        for (int i = 0; i < M.length; i++) {
+            if (M[i][i] == 1) {
+                dfs(M, i);
+                num++;
+            }
+        }
+        return num;
+    }
+
+    /**
+     * M[i][i] = 0表示第i个人我们已经访问过了
+     * 访问过的人无需重复访问
+     */
+    private void dfs(int[][] M, int i) {
+        M[i][i] = 0;
+        for (int j = 0; j < M.length; j++) {
+            if (M[j][j] != 0 && M[i][j] == 1) {
+                dfs(M, j);
+            }
+        }
+    }
+}

leetcode/src/Main.java

@@ -2,32 +2,26 @@
 
 public class Main {
 
-    public static int totalFruit(int[] tree) {
-        int max = 0;
-        HashMap<Integer, Integer> map = new HashMap<>();
-        for (int i = 0, j = 0; j < tree.length; j++) {
-            int value = tree[j];
-
-            map.put(value, map.getOrDefault(value, 0) + 1);
-
-            for ( ; map.size() > 2; i++) {
-                int val = tree[i], cnt = map.get(val);
-                if (cnt == 1) {
-                    map.remove(val);
-                } else {
-                    map.put(val, cnt - 1);
-                }
+    public int findCircleNum(int[][] M) {
+        int num = 0;
+        for (int i = 0; i < M.length; i++) {
+            if (M[i][i] == 1) {
+                dfs(M, i);
+                num++;
             }
-            max = Math.max(max, j - i + 1);
         }
+        return num;
+    }
 
-        return max;
+    private void dfs(int[][] M, int i) {
+        M[i][i] = 0;
+        for (int j = 0; j < M.length; j++) {
+            if (M[j][j] != 0 && M[i][j] == 1) {
+                dfs(M, j);
+            }
+        }
     }
 
     public static void main(String[] args) {
-        int n = totalFruit(new int[]{
-                1, 2, 1
-        });
-        System.out.println(n);
     }
 }