2017 ACM-ICPC 亚洲区（乌鲁木齐赛区）网络赛 H. Skiing

#include<algorithm>

#include<iostream>

#include<cstring>

#include<cstdio>

#include<queue>

using namespace std;

#define MP make_pair

const int N = 100000 + 10;

const int INF = 0x3f3f3f3f;

 

vector<pair<int, int> > edge[N];

 

 

class Topological{

private:

    int tot = 0, vis[N], n;

    queue<int> Q;

public:

    int in[N], dist[N], topo[N];

    void Init(int n){

        this -> n = n;

        for(int i = 1; i <= n; ++ i)

            vis[i] = 0, dist[i] = - INF;

    }

    bool Topo_Sort(){   //拓扑排序

        for(int i = 1; i <= n; ++ i){

            if(in[i] == 0){

                Q.push( i );

                vis[i] = true;

                dist[i] = 0;

                topo[tot++] = i;

            }

        }

        while(!Q.empty()){

            int u = Q.front(); Q.pop();

            for(int i = edge[u].size() - 1; i >= 0; -- i){

                int v = edge[u][i].first;

                -- in[v];

                if(in[v] == 0 && !vis[v]){

                    vis[v] = true;

                    Q.push( v );

                    topo[tot++] = v;

                }

            }

        }

        return tot == n ? true : false;

    }

    int Get_Cpm(){   //求关键路径

        for(int i = 0; i < tot; ++ i){

            int u = topo[i];

            for(int j = edge[u].size() - 1; j >= 0; -- j){

                int v = edge[u][j].first;

                int c = edge[u][j].second;

                if(dist[v] < dist[u] + c) dist[v] = dist[u] + c;

            }

        }

        int ans = 0;

        for(int i = 1; i <= n; i++)

            if(dist[i] > ans) ans = dist[i];

        return ans;

    }

}Topo;

void Input_data(int &n, int &m){

    int u, v, c;

    scanf("%d %d", &n, &m);

    Topo.Init( n );

    for(int i = 1; i <= m; ++ i){

        scanf("%d %d %d", &u, &v, &c);

        edge[u].push_back(MP(v, c));

        ++ Topo.in[v];

    }

}

int main(){

    int T, n, m;

    scanf("%d", &T);

    while(T --){

        Input_data(n, m);

        Topo.Topo_Sort();

        printf("%d\n", Topo.Get_Cpm());

        for(int i = 1; i <= n; ++ i) edge[i].clear();

    }

}