feat: solve DaleStudy#261 in python

course-schedule/EGON.py

@@ -0,0 +1,58 @@
+from collections import deque
+from typing import List
+from unittest import TestCase, main
+
+
+class Solution:
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        return self.solve_topological_sort(numCourses, prerequisites)
+
+    """
+    Runtime: 1 ms (Beats 100.00%)
+    Time Complexity: o(c + p)
+        - graph 및 rank 갱신에 prerequisites의 길이 p만큼 조회하는데 O(p)
+        - queue의 초기 노드 삽입에 numCourses만큼 조회하는데 O(c)
+        - queue에서 위상 정렬로 탐색하는데 모든 노드와 간선을 조회하는데 O(c + p)
+        > O(p) + O(c) + O(c + p) ~= o(c + p)
+
+    Memory: 17.85 MB (Beats 99.94%)
+    Space Complexity: O(c)
+        - graph 변수 사용에 O(c)
+        - rank 변수 사용에 O(c)
+        - queue 변수 사용에서 최대 크기는 graph의 크기와 같으므로 O(c)
+        > O(c) + O(c) + O(c) ~= O(c)
+    """
+    def solve_topological_sort(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        graph = {i: [] for i in range(numCourses)}
+        rank = [0] * numCourses
+        for u, v in prerequisites:
+            graph[v].append(u)
+            rank[u] += 1
+
+        queue = deque()
+        for i in range(numCourses):
+            if rank[i] == 0:
+                queue.append(i)
+
+        count = 0
+        while queue:
+            node = queue.popleft()
+            count += 1
+            for neighbor in graph[node]:
+                rank[neighbor] -= 1
+                if rank[neighbor] == 0:
+                    queue.append(neighbor)
+
+        return count == numCourses
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        numCourses = 5
+        prerequisites = [[1,4],[2,4],[3,1],[3,2]]
+        output = True
+        self.assertEqual(Solution.canFinish(Solution(), numCourses, prerequisites), output)
+
+
+if __name__ == '__main__':
+    main()