22

547.java

@@ -0,0 +1,22 @@
+public class Solution {
+    public int findCircleNum(int[][] M) {
+        boolean visited[] = new boolean[M.length];
+        int cycle = 0;
+        for(int i = 0; i < M.length; i ++){
+            if(!visited[i]){
+                cycle++;
+                visited[i] = true;
+                dfs(M, visited, i);//dfs to mark all ppl in the cycle visited
+            }
+        }
+        return cycle;
+    }
+    public void dfs(int[][] M, boolean[] visited, int i){
+        for(int j = 0; j < M[0].length; j++){//no return case here!!
+            if(!visited[j] && M[i][j] == 1){
+                visited[j] = true;
+                dfs(M, visited, j);
+            }
+        }
+    }
+}

547_2.java

@@ -0,0 +1,23 @@
+public class Solution{
+
+  public  int findCircleNum(int [][] M){
+    boolean visited[] = new boolean[M.length];
+    int cycle = 0;
+    for(int i  =0; i<M.length;i++){
+      if(!visited[i]){
+        cycle++;
+        visited[i] = true;
+        dfs(M,visited,i);
+      }
+    }
+    return cycle;
+  }
+  public void dfs(int[][] M,boolean[] visited,int i){
+    for(int j = 0;j<M[0].length;j++){
+      if(!visited[j] && M[i][j] ==1){
+        visited[j] = true;
+        dfs(M,visited,j);
+      }
+    }
+  }
+}