Solve 210 with Python

Author: illuz

solutions/210.Course_Schedule_II/AC_stack_v+e.py

@@ -0,0 +1,35 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+# Author:      illuz <iilluzen[at]gmail.com>
+# File:        AC_stack_v+e.py
+# Create Date: 2016-02-25 19:31:07
+# Usage:       AC_stack_v+e.py 
+# Descripton:  just as the 207
+
+class Solution:
+    # @param {integer} numCourses
+    # @param {integer[][]} prerequisites
+    # @return {boolean}
+    def findOrder(self, numCourses, prerequisites):
+        # in order and reverse order
+        graph = collections.defaultdict(set)
+        rev = collections.defaultdict(set)
+
+        for cur, pre in prerequisites:
+            graph[cur].add(pre)
+            rev[pre].add(cur)
+
+        # get the 0 in-order nodes into the stack
+        stack = [n for n in range(numCourses) if not graph[n]]
+        path = []
+        cnt = 0
+        while stack:
+            node = stack.pop()
+            path.append(node)
+            cnt += 1
+            for pre in rev[node]:
+                graph[pre].remove(node)
+                if not graph[pre]:
+                    stack.append(pre)
+        return path if cnt == numCourses else []
+