【HDOJ】3696 Farm Game

SPFA求最短路径。见图的时候注意逆向建图。

 /* 3696 */
 #include <iostream>
 #include <queue>
 #include <vector>
 #include <algorithm>
 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <cstdlib>
 using namespace std;

 #define MAXN 10005
 #define MAXV 10005
 #define MAXE 50005

 typedef struct {
     int v, next;
     double r;
 } Edge_t;

 const double INF = .;
 Edge_t E[MAXE];
 int L, head[MAXN];
 double w[MAXN], p[MAXN];
 double rate[MAXN];
 bool visit[MAXN];
 int n, m;

 void addEdge(int u, int v, double r) {
     E[L].v = v;
     E[L].next = head[u];
     E[L].r = r;
     head[u] = L++;
 }

 void init() {
     memset(head, -, sizeof(int)*(n+));
     L = ;
 }

 void spfa(int u) {
     int i, j, k, v;
     queue<int> Q;

     for (i=; i<=n; ++i)
         rate[i] = -INF;
     memset(visit, false, sizeof(visit));
     rate[u] = 0.0;
     visit[u] = true;
     Q.push(u);

     while (!Q.empty()) {
         u = Q.front();
         Q.pop();
         visit[u] = false;
         for (i=head[u]; i!=-; i=E[i].next) {
             v = E[i].v;
             if (rate[v] < rate[u]+E[i].r) {
                 rate[v] = rate[u] + E[i].r;
                 if (!visit[v]) {
                     visit[v] = true;
                     Q.push(v);
                 }
             }
         }
     }
 }

 int main() {
     int i, j, k;
     int u, v;
     double r, ans;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     while (scanf("%d",&n)!=EOF && n) {
         init();
         for (i=; i<=n; ++i) {
             scanf("%lf %lf", &p[i], &w[i]);
             addEdge(, i, log(p[i]));
         }
         scanf("%d", &m);
         while (m--) {
             scanf("%d %d", &k, &u);
             --k;
             while (k--) {
                 scanf("%lf %d", &r, &v);
                 addEdge(v, u, log(r));
                 u = v;
             }
         }
         spfa();
         ans = 0.0;
         for (i=; i<=n; ++i) {
             r = exp(rate[i]);
             if (p[i] < r)
                 p[i] = r;
             ans += p[i]*w[i];
         }
         printf("%.2lf\n", ans);
     }

     return ;
 }