1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87

#include <iostream>
#include <vector>
#include <queue>
#include <unordered_set>

class Solution {
    std::vector<int> tpsort(int n, std::vector<std::vector<int>> adj) {
        std::vector<int> res;
        std::vector<int> inDegree(n, 0);
        for (int i = 0; i < n; ++i) {
            for (int j : adj[i]) {
                ++inDegree[j];
            }
        }
        
        std::queue<int> q;
        for (int i = 0; i < n; ++i) {
            if (inDegree[i] == 0) {
                q.push(i);
            }
        }
        
        while (!q.empty()) {
            int u = q.front();
            q.pop();
            res.push_back(u);
            for (int v : adj[u]) {
                --inDegree[v];
                if (inDegree[v] == 0) {
                    q.push(v);
                }
            }
        }
        
        if (res.size() != n) {
            return {};
        }
        return res;
    }
    
public:
    std::vector<int> sortItems(int n, int m, std::vector<int>& group, std::vector<std::vector<int>>& beforeItems) {
        for (int i = 0; i < n; ++i) {
            if (group[i] == -1) {
                group[i] = m++;
            }
        }
        
        std::vector<std::vector<int>> adjg(m);
        std::vector<std::vector<int>> adji(n);
        std::unordered_set<int> edges;
        for (int i = 0; i < n; ++i) {
            int gb = group[i];
            for (int j : beforeItems[i]) {
                int ga = group[j];
                adji[j].push_back(i);
                int edge = (gb << 16) + ga;
                if (ga != gb && !edges.count(edge)) {
                    adjg[ga].push_back(gb);
                    edges.insert(edge);
                }
            }
        }
        
        std::vector<int> gorder = tpsort(m, adjg);
        if (gorder.size() < m) {
            return {};
        }
        std::vector<int> iorder = tpsort(n, adji);
        if (iorder.size() < n) {
            return {};
        }
        
        std::vector<std::vector<int>> g2i(m);
        for (int i : iorder) {
            g2i[group[i]].push_back(i);
        }
        std::vector<int> res;
        res.reserve(n);
        for (auto& g : gorder) {
            for (int i : g2i[g]) {
                res.push_back(i);
            }
        }
        return res;
    }
};