- Course Schedule DaleStudy#261

Author: ayosecu

course-schedule/ayosecu.py

@@ -0,0 +1,44 @@
+from typing import List
+from collections import defaultdict, deque
+
+class Solution:
+    """
+        - Time Complexity: O(N + P), N = numCourses, P = len(prerequisites) 
+        - Space Complexity: O(N + P)
+    """
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        # Topology Sort
+        # BFS based, ingress count, visited
+        ingress_cnt = [0] * numCourses
+        dic = defaultdict(list)
+
+        for dst, src in prerequisites:
+            ingress_cnt[dst] += 1
+            dic[src].append(dst)
+
+        dq = deque([])            
+        for dst in range(numCourses):
+            if ingress_cnt[dst] == 0:
+                dq.append(dst)
+
+        visited_count = 0
+        while dq:
+            src = dq.popleft()
+            visited_count += 1
+
+            for dst in dic[src]:
+                ingress_cnt[dst] -= 1
+                if ingress_cnt[dst] == 0:
+                    dq.append(dst)
+        
+        return visited_count == numCourses
+    
+tc = [
+        (2, [[1,0]], True),
+        (2, [[1,0],[0,1]], False)
+]
+
+sol = Solution()
+for i, (n, p, e) in enumerate(tc, 1):
+    r = sol.canFinish(n, p)
+    print(f"TC {i} is Passed!" if r == e else f"TC {i} is Failed! - Expected: {e}, Result: {r}")