add 210

Author: fishercoder1534

Diff for: README.md

@@ -1241,7 +1241,7 @@ _If you like this project, please leave me a star._ ★
 | 213  | [House Robber II](https://leetcode.com/problems/house-robber-ii/)                                                                                                                             | [Solution](../master/src/main/java/com/fishercoder/solutions/_213.java)                                                                  |                                                                               | Medium                           | DP                                                                   
 | 212  | [Word Search II](https://leetcode.com/problems/word-search-ii/)                                                                                                                               | [Solution](../master/src/main/java/com/fishercoder/solutions/WordSearchII.java)                                                          |                                                                               | Hard                             | Trie                                                                 
 | 211  | [Add and Search Word - Data structure design](https://leetcode.com/problems/add-and-search-word-data-structure-design/)                                                                       | [Solution](../master/src/main/java/com/fishercoder/solutions/_211.java)                                                                  |                                                                               | Medium                           | Trie                                                                 
-| 210  | [Course Schedule II](https://leetcode.com/problems/course-schedule-ii/)                                                                                                                       | [Solution](../master/src/main/java/com/fishercoder/solutions/_210.java)                                                                  |                                                                               | Medium                           |
+| 210  | [Course Schedule II](https://leetcode.com/problems/course-schedule-ii/)                                                                                                                       | [Solution](../master/src/main/java/com/fishercoder/solutions/_210.java)                                                                  |                                                                               | Medium                           | Adjacency List, BFS, Topological Sort
 | 209  | [Minimum Size Subarray Sum](https://leetcode.com/problems/minimum-size-subarray-sum/)                                                                                                         | [Solution](../master/src/main/java/com/fishercoder/solutions/_209.java)                                                                  |                                                                               | Medium                           |
 | 208  | [Implement Trie](https://leetcode.com/problems/implement-trie-prefix-tree/)                                                                                                                   | [Solution](../master/src/main/java/com/fishercoder/solutions/_208.java)                                                                  | [:tv:](https://youtu.be/Br7Wt4V5o1c)                                          | Medium                           | Trie                                                                 
 | 207  | [Course Schedule](https://leetcode.com/problems/course-schedule/)                                                                                                                             | [Solution](../master/src/main/java/com/fishercoder/solutions/_207.java)                                                                  |                                                                               | Medium                           |

Diff for: src/main/java/com/fishercoder/solutions/_210.java

@@ -0,0 +1,44 @@
+package com.fishercoder.solutions;
+
+import java.util.*;
+
+public class _210 {
+    public static class Solution1 {
+        public int[] findOrder(int numCourses, int[][] prerequisites) {
+            int[] indegree = new int[numCourses];
+            Map<Integer, List<Integer>> adjacencyList = new HashMap<>();
+            for (int[] pre : prerequisites) {
+                int src = pre[1];
+                int dest = pre[0];
+                List<Integer> list = adjacencyList.getOrDefault(src, new ArrayList<>());
+                list.add(dest);
+                adjacencyList.put(src, list);
+                indegree[src]++;
+            }
+            Queue<Integer> q = new LinkedList<>();
+            for (int i = 0; i < numCourses; i++) {
+                if (indegree[i] == 0) {
+                    q.offer(i);
+                }
+            }
+            int[] order = new int[numCourses];
+            int i = 0;
+            while (!q.isEmpty()) {
+                Integer course = q.poll();
+                order[i++] = course;
+                if (adjacencyList.containsKey(course)) {
+                    for (int neighbor : adjacencyList.get(course)) {
+                        indegree[neighbor]--;
+                        if (indegree[neighbor] == 0) {
+                            q.offer(neighbor);
+                        }
+                    }
+                }
+            }
+            if (i == numCourses) {
+                return order;
+            }
+            return new int[]{};
+        }
+    }
+}