[算法与数据结构][图算法][拓扑排序]尝试1

Posted 2021-05-23 xcy6666

#include<utility> //pair
#include<vector>
#include<set> // multiset
#include<iostream>
/*
   1

   2 -> 1

     /- 6
   4 -- 3 -- 1
   5 -- 2 -/

   2 -> 1 -> 3 -> 2

*/
using namespace std;

vector<vector<int>> adj_list;
typedef pair<int, int> id_in_d; //id, in degree
//typedef custom_comp function<bool(id_in_d, id_in_d)>
auto custom_cmp = [](id_in_d a, id_in_d b){ return a.second < b.second; };
multiset<id_in_d, decltype(custom_cmp)> nodes(custom_cmp);
void construct(){
        adj_list.resize(6+1);

        //adj_list[2].push_back(1);

        adj_list[4].push_back(6);
        adj_list[4].push_back(3);
        adj_list[3].push_back(1);
        adj_list[5].push_back(2);
        adj_list[2].push_back(1);
        //time: O(E), space O(E)

        //look up; remove; insert
        // time:  O(E*log_V) + O(E*log_V)
        // space: O(V)
        nodes.insert({6,1});
        nodes.insert({3,1});
        nodes.insert({1,2});
        nodes.insert({2,1});
        nodes.insert({4,0});
        nodes.insert({5,0});

        auto it = nodes.find({3,1});
        cout << it->first << " " << it->second << endl;
}

void topo_sort(){
        vector<int> res;
        int id;
        while(nodes.size() > 0 && nodes.begin()->second == 0){
                id = nodes.begin()->first;
                res.push_back(id);
                nodes.erase(nodes.begin());
                for(auto nbr : adj_list[id]){

                }
        }
}


int main(){
    construct();
    return 0;
}

/* fail to construct a data structure that can:
 *      store {id, degree}
 *      quick find minimal degree
 *      quick update degree
 *
 *      vector<int> degree; //offset as id
 *      map<int, set<int>> deg_ids; //indexed by degree
 */