210.课程表Ⅱ

思路类似207，只需要增加一个数组存放入度=0的课程顺序即可

class Solution {
public:
    vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {
        vector<int> indeg(numCourses);
        vector<vector<int>> course(numCourses);
        queue<int> zero;
        vector<int> sequence;

        for(int i =0;i<prerequisites.size();i++)
        {
            indeg[prerequisites[i][0]]++;
            course[prerequisites[i][1]].push_back(prerequisites[i][0]);
        }

        for(int i = 0;i<numCourses;i++)
        {
            if(indeg[i]==0)
                zero.push(i);
        }

        while(zero.size()!=0)
        {
            int pre = zero.front();
            zero.pop();
            numCourses--;
            sequence.push_back(pre);

            for(int i=0;i<course[pre].size();i++)
            {
                indeg[course[pre][i]]--;
                if(indeg[course[pre][i]]==0)
                    zero.push(course[pre][i]);
            }
        }

        vector<int> no;
        if(numCourses == 0)
            return sequence;
        else return no;


    }
};