8.13日一个简单的拓扑排序

[是泡泡]

class Solution {
public:
    bool canFinish(int n, vector<vector<int>>& p) {
        vector<vector<int>> g(n);
        vector<int> d(n);
        for(auto &i: p)
        {
            int x = i[0], y = i[1];
            g[x].push_back(y);
            d[y]++;
        }
        queue<int> q;
        int ans = 0;
        for(int i = 0; i < n; i++)
            if(!d[i]) q.push(i);
        while(q.size())
        {
            auto t = q.front();
            q.pop();
            ans++;
            for(auto &i: g[t])
                if(--d[i] == 0) q.push(i);
            
        }
        return ans == n;
    }
};