diff --git a/data/progress.txt b/data/progress.txt
index 67ac9a1a..1a9fc3a2 100644
--- a/data/progress.txt
+++ b/data/progress.txt
@@ -1,3 +1,4 @@
+20240519: 207
 20240518: 213(todo),198(todo),212(todo),211,338,208(again)
 20240517: 347,253(todo),91(todo),217
 20240516: 226,98,253(todo)
diff --git a/data/to_review.txt b/data/to_review.txt
index e03588ea..54fa59b3 100644
--- a/data/to_review.txt
+++ b/data/to_review.txt
@@ -1,4 +1,4 @@
-2024-07-12 -> ['213(todo),198(todo),212(todo),211,338']
+2024-07-12 -> ['213(todo),198(todo),212(todo),211,338,208(again)']
 2024-07-11 -> ['347,253(todo),91(todo),217']
 2024-07-10 -> ['226,98,253(todo)']
 2024-07-09 -> ['104,230,102,100']
@@ -7,7 +7,7 @@
 2024-07-06 -> ['371']
 2024-07-05 -> ['121,252']
 2024-07-04 -> ['125']
-2024-06-21 -> ['213(todo),198(todo),212(todo),211,338']
+2024-06-21 -> ['213(todo),198(todo),212(todo),211,338,208(again)']
 2024-06-20 -> ['347,253(todo),91(todo),217']
 2024-06-19 -> ['226,98,253(todo)']
 2024-06-18 -> ['104,230,102,100']
@@ -16,7 +16,7 @@
 2024-06-15 -> ['371']
 2024-06-14 -> ['121,252']
 2024-06-13 -> ['125']
-2024-06-08 -> ['213(todo),198(todo),212(todo),211,338']
+2024-06-08 -> ['213(todo),198(todo),212(todo),211,338,208(again)']
 2024-06-07 -> ['347,253(todo),91(todo),217']
 2024-06-06 -> ['226,98,253(todo)']
 2024-06-05 -> ['104,230,102,100']
@@ -24,19 +24,19 @@
 2024-06-03 -> ['242,235']
 2024-06-02 -> ['371']
 2024-06-01 -> ['121,252']
-2024-05-31 -> ['213(todo),198(todo),212(todo),211,338', '125']
+2024-05-31 -> ['213(todo),198(todo),212(todo),211,338,208(again)', '125']
 2024-05-30 -> ['347,253(todo),91(todo),217']
 2024-05-29 -> ['226,98,253(todo)']
 2024-05-28 -> ['104,230,102,100']
 2024-05-27 -> ['105,106']
-2024-05-26 -> ['213(todo),198(todo),212(todo),211,338', '242,235']
+2024-05-26 -> ['213(todo),198(todo),212(todo),211,338,208(again)', '242,235']
 2024-05-25 -> ['347,253(todo),91(todo),217', '371']
 2024-05-24 -> ['226,98,253(todo)', '121,252']
-2024-05-23 -> ['213(todo),198(todo),212(todo),211,338', '104,230,102,100', '125']
+2024-05-23 -> ['213(todo),198(todo),212(todo),211,338,208(again)', '104,230,102,100', '125']
 2024-05-22 -> ['347,253(todo),91(todo),217', '105,106']
-2024-05-21 -> ['213(todo),198(todo),212(todo),211,338', '226,98,253(todo)', '242,235']
-2024-05-20 -> ['213(todo),198(todo),212(todo),211,338', '347,253(todo),91(todo),217', '104,230,102,100', '371']
-2024-05-19 -> ['213(todo),198(todo),212(todo),211,338', '347,253(todo),91(todo),217', '226,98,253(todo)', '105,106', '121,252']
+2024-05-21 -> ['213(todo),198(todo),212(todo),211,338,208(again)', '226,98,253(todo)', '242,235']
+2024-05-20 -> ['213(todo),198(todo),212(todo),211,338,208(again)', '347,253(todo),91(todo),217', '104,230,102,100', '371']
+2024-05-19 -> ['213(todo),198(todo),212(todo),211,338,208(again)', '347,253(todo),91(todo),217', '226,98,253(todo)', '105,106', '121,252']
 2024-05-18 -> ['347,253(todo),91(todo),217', '226,98,253(todo)', '104,230,102,100', '242,235', '125']
 2024-05-17 -> ['226,98,253(todo)', '104,230,102,100', '105,106', '371']
 2024-05-16 -> ['104,230,102,100', '105,106', '242,235', '121,252']
@@ -211,7 +211,7 @@
 2023-08-29 -> ['131,17', '40', '1448', '113,257']
 2023-08-28 -> ['131,17', '90', '199']
 2023-08-27 -> ['79', '46', '112']
-2023-08-26 -> ['40', '78,39', '572,235', '207']
+2023-08-26 -> ['207', '40', '78,39', '572,235']
 2023-08-25 -> ['79', '90', '355', '2,146', '404']
 2023-08-24 -> ['79', '40', '46', '621', '138']
 2023-08-23 -> ['79', '40', '90', '981,143']
@@ -231,7 +231,7 @@
 2023-08-08 -> ['1448', '452', '113,257']
 2023-08-07 -> ['33', '208,211', '199', '617']
 2023-08-06 -> ['230,105', '875,153', '112']
-2023-08-05 -> ['098', '572,235', '853,74', '207', '543,572']
+2023-08-05 -> ['207', '098', '572,235', '853,74', '543,572']
 2023-08-04 -> ['208,211', '2,146', '739,150,22', '404']
 2023-08-03 -> ['230,105', '1448', '138']
 2023-08-02 -> ['208,211', '098', '199', '981,143']
@@ -244,7 +244,7 @@
 2023-07-26 -> ['199', '572,235', '138', '452', '113,257']
 2023-07-25 -> ['33', '572,235', '2,146', '981,143']
 2023-07-24 -> ['572,235', '2,146', '138', '875,153', '567,155', '112']
-2023-07-23 -> ['2,146', '138', '981,143', '452', '853,74', '19', '207']
+2023-07-23 -> ['207', '2,146', '138', '981,143', '452', '853,74', '19']
 2023-07-22 -> ['33', '138', '981,143', '739,150,22', '128,167,3,424', '404', '687']
 2023-07-21 -> ['981,143', '452', '875,153', '36,271', '637,653', '1047']
 2023-07-20 -> ['33', '452', '853,74', '347']
@@ -252,18 +252,18 @@
 2023-07-18 -> ['33', '875,153', '853,74', '19', '113,257']
 2023-07-17 -> ['875,153', '853,74', '739,150,22', '128,167,3,424', '104,110', '617']
 2023-07-16 -> ['853,74', '739,150,22', '567,155', '36,271', '112']
-2023-07-15 -> ['739,150,22', '19', '347', '207', '162', '543,572']
+2023-07-15 -> ['207', '739,150,22', '19', '347', '162', '543,572']
 2023-07-14 -> ['567,155', '128,167,3,424', '404', '496']
 2023-07-13 -> ['567,155', '19', '36,271', '113,257']
 2023-07-12 -> ['567,155', '19', '128,167,3,424', '347']
 2023-07-11 -> ['19', '128,167,3,424', '36,271', '112']
-2023-07-10 -> ['128,167,3,424', '36,271', '347', '113,257', '207', '160,203']
+2023-07-10 -> ['207', '128,167,3,424', '36,271', '347', '113,257', '160,203']
 2023-07-09 -> ['36,271', '347', '404', '104,110', '687', '1353,21,24']
 2023-07-08 -> ['347', '113,257', '112', '637,653', '101']
-2023-07-07 -> ['113,257', '207', '162', '067']
+2023-07-07 -> ['207', '113,257', '162', '067']
 2023-07-06 -> ['113,257', '112', '404']
-2023-07-05 -> ['112', '207']
-2023-07-04 -> ['112', '207', '404', '104,110', '617']
+2023-07-05 -> ['207', '112']
+2023-07-04 -> ['207', '112', '404', '104,110', '617']
 2023-07-03 -> ['207', '404']
 2023-07-02 -> ['404', '162', '543,572', '038']
 2023-07-01 -> ['104,110', '687', '674']
diff --git a/leetcode_java/src/main/java/LeetCodeJava/BFS/CourseSchedule.java b/leetcode_java/src/main/java/LeetCodeJava/BFS/CourseSchedule.java
index 3c571bae..44fb5bb0 100644
--- a/leetcode_java/src/main/java/LeetCodeJava/BFS/CourseSchedule.java
+++ b/leetcode_java/src/main/java/LeetCodeJava/BFS/CourseSchedule.java
@@ -167,6 +167,26 @@ public boolean canFinish_0_2(int numCourses, int[][] prerequisites) {
     }
 
     private boolean dfs(List<Integer> res, Map<Integer, List<Integer>> graph, int[] visited, int course) {
+
+        /** NOTE !!!
+         *
+         *  here we maintain 3 status:
+         *
+         *   status = 0 : not visited
+         *   status = 1 : visiting
+         *   status = 2 : visited
+         *
+         *   ->
+         *   So,
+         *   if status == 2, return true directly, since such course already been visited, we should not visit it again
+         *
+         *   if status = 1, should return false directly, since "it is being visiting now",
+         *                  any other progress try to visit the same course at the same time
+         *                  means course conflict, -> can't take such course
+         *
+         *
+         *  Ref : https://github.com/yennanliu/CS_basics/blob/master/leetcode_python/Breadth-First-Search/course-schedule.py#L44
+         */
         if (visited[course] == 1) {
             return false;
         }
diff --git a/leetcode_java/src/main/java/dev/workspace3.java b/leetcode_java/src/main/java/dev/workspace3.java
index c7428537..582702ee 100644
--- a/leetcode_java/src/main/java/dev/workspace3.java
+++ b/leetcode_java/src/main/java/dev/workspace3.java
@@ -802,4 +802,77 @@ public boolean startsWith(String prefix) {
         }
     }
 
+    // LC 207
+    // dfs ?
+    // 0930 am
+    /**
+     *  prerequisites[i] = [ai, bi]
+     *  indicates that
+     *  you must take course "bi" first
+     *  if you want to take course "ai"
+     */
+    public boolean canFinish(int numCourses, int[][] prerequisites) {
+
+         if (numCourses == 0 && prerequisites.length == 0){
+             return true;
+         }
+
+        if (prerequisites.length == 0){
+            return true;
+        }
+
+         Map<Integer, List<Integer>> map = new HashMap<>();
+
+         for (int[] x : prerequisites){
+             if (!map.containsKey(x[0])){
+                 List<Integer> cur = new ArrayList<>();
+                 cur.add(x[1]);
+                 map.put(x[0], cur);
+             }else{
+                 List<Integer> cur = map.get(x[0]);
+                 cur.add(x[1]);
+                 map.put(x[0], cur);
+             }
+         }
+
+         System.out.println("map = " + map);
+
+         int[] visited = new int[numCourses];
+         for (int i = 0; i < numCourses; i++){
+             visited[i] = 0;
+         }
+
+         for (int i = 0; i < numCourses; i++){
+             if (! this._help_check(i, visited, map)){
+                 return false;
+             }
+         }
+
+         return true;
+        //return Arrays.stream(visited).sum() == numCourses;
+    }
+
+    public boolean _help_check(int courseId, int[] visited, Map<Integer, List<Integer>> map){
+
+        System.out.println("---> courseId = " + courseId + " map = " + map + " visited = " + visited);
+
+        if (!map.containsKey(courseId)){
+            return true;
+        }
+
+        for (int val : map.get(courseId)){
+            if (visited[courseId] == 1){
+                return false;
+            }
+            if (courseId == val){
+                return false;
+            }
+            visited[courseId] = 1;
+            this._help_check(val, visited, map);
+            visited[courseId] = 0;
+        }
+
+        return true;
+    }
+
 }