• hdu 4784 Dinner Coming Soon


                spfa+优先队列。刚开始只用的spfa,结果tle到死。然后听队友说要用到优先队列,想了想,对时间分层的话的确每一个结点都只进队列一次即可,因为只有大时间才能更新出小时间,然后就wa成shi了。按队友写的改了才过得,好伤心的说,这是好题。。。

                附上代码供大家对拍吧。

    #include<algorithm>
    #include<iostream>
    #include<cstring>
    #include<cstdio>
    #include<vector>
    #include<queue>
    #include<cmath>
    #define LL long long
    #define CLR(a, b) memset(a, b, sizeof(a))
    #define REP(i, n) for(int i = 0; i < n; i ++)
    #define FF(i, a, b) for(int i = a; i < b; i ++)
    #define FD(i, a, b) for(int i = a; i >= b; i --)
    #define swp(a, b) a^=b^=a^=b;
    
    using namespace std;
    
    struct Node
    {
        int u, b, vd, t;
        Node(){}
        Node(int a, int b, int c, int d):u(a), b(b), vd(c), t(d){}
        bool operator < (const Node &rhs) const
        {
            return t < rhs.t;
        }
    };
    
    struct Edge
    {
        int u, v, t, m;
        Edge(){}
        Edge(int a, int b, int c, int d):u(a), v(b), t(c), m(d){}
    }E[420];
    
    int fir[220], next[440], tot;
    
    void Add_Edge(int u, int v, int t, int m)
    {
        E[tot] = Edge(u, v, t, m);
        next[tot] = fir[u]; fir[u] = tot ++;
    }
    
    int dp[110][6][7][220];
    bool vis[110][6][7][220];
    int p[110][7];
    int N, M, B, K, R, T;
    
    priority_queue<Node>q;
    
    void relax(int u, int b, int vd, int t, int val)
    {
        if ((u == 1 || u == N) && vd != 0) return ;
        if(dp[u][b][vd][t] < val)
        {
            dp[u][b][vd][t] = val;
            if(!vis[u][b][vd][t])
            {
                Node w = Node(u, b, vd, t);
                q.push(w);
                vis[u][b][vd][t] = true;
            }
        }
    }
    
    void spfa()
    {
        int u, v, m, t,vd, b;
        Node a = Node(1, 0, 0, T);
        CLR(dp, -1);CLR(vis, false);
        dp[1][0][0][T] = R;
        vis[1][0][0][T] = true;
        q.push(a);
        while(!q.empty())
        {
            a = q.top();q.pop();
            u = a.u;b = a.b;vd = a.vd;t = a.t;
            if(u == N) continue;
            if(t > 0)
            {
                int val = dp[u][b][vd][t];
                relax(u, b, (vd + 1) % K, t - 1, val);
                if(p[u][vd] != -1)
                {
                    if(b > 0)
                    {
                        relax(u, b - 1, (vd + 1) % K, t - 1, val + p[u][vd]);
                    }
                    if(b < B && val >= p[u][vd])
                    {
                        relax(u, b + 1, (vd + 1) % K, t - 1, val - p[u][vd]);
                    }
                }
            }
            for(int i = fir[u]; ~i; i = next[i])
            {
                int tmp = t - E[i].t;
                if(tmp < 0) continue;
                v = E[i].v;
                int val = dp[u][b][vd][t] - E[i].m;
                if(val < 0) continue;
                relax(v, b, vd, tmp, val);
                if(p[u][vd] != -1)
                {
                    if(b > 0)
                    {
                        relax(v, b - 1, vd, tmp, val + p[u][vd]);
                    }
                    if(b < B && val >= p[u][vd])
                    {
                        relax(v, b + 1, vd, tmp, val - p[u][vd]);
                    }
                }
            }
        }
    }
    
    int main()
    {
        int Time, cas = 1;
        scanf("%d", &Time);
        while(Time --)
        {
            scanf("%d%d%d%d%d%d", &N, &M, &B, &K, &R, &T);
            for(int i = 0; i < K; i ++)
            {
                for(int j = 1; j <= N; j ++)
                {
                    scanf("%d", &p[j][i]);
                }
            }
            CLR(fir, -1);tot = 0;
            int u, v, t, m;
            for(int i = 0; i < M; i ++)
            {
                scanf("%d%d%d%d", &u, &v, &t, &m);
                Add_Edge(u, v, t, m);
            }
            spfa();
            int ans = -1;
            for(int i = 0; i <= B; i ++)
            {
                for(int j = 0; j <= T; j ++)
                {
                    ans = max(ans, dp[N][i][0][j]);
                }
            }
            if(ans != -1) printf("Case #%d: %d
    ", cas ++, ans);
            else printf("Case #%d: Forever Alone
    ", cas ++);
        }
    }
    


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  • 原文地址:https://www.cnblogs.com/riasky/p/3431168.html
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