亚麻：Course Schedule II

 

这是亚麻的OA题，

leetcode链接。https://leetcode.com/problems/course-schedule-ii/description/

the code listed here has passed all the test case in leetcode.

 

// key point 
// use the vector< pre, vector<independents courses> > to create graph
// use vector< indegree  > to record the node of the incomming degrees
// use queue to BFS. 

        vector<int> res;
        vector<vector<int> > graph(numCourses, vector<int>(0));
        vector<int> in(numCourses, 0);
        for (auto &a : prerequisites) {
            graph[a.second].push_back(a.first);
            ++in[a.first];
        }
        queue<int> q;
        for (int i = 0; i < numCourses; ++i) {
            if (in[i] == 0) q.push(i);
        }
        while (!q.empty()) {
            int t = q.front();
            res.push_back(t);
            q.pop();
            for (auto &a : graph[t]) {
                --in[a];
                if (in[a] == 0) q.push(a);
            }
        }
        if (res.size() != numCourses) res.clear();
        return res;