POJ_2253 Frogger 【最短路变形】

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <queue>
 6 #include <fstream>
 7 using namespace std;
 8 #define INF 0x3f3f3f3f
 9 typedef pair<double, int> P;
10 const int MAXN = 2e2 + 14;
11 struct point
12 {
13     int x, y;
14 }node[MAXN];
15 struct cmp
16 {
17     bool operator()(const P &a, const P &b)
18     {
19         return a.first > b.first;
20     }
21 };
22 int n;
23 double G[MAXN][MAXN];
24 double dist[MAXN];
25 bool flag[MAXN];
26 
27 void Dijkstra(int s)
28 {
29     priority_queue<P, vector<P>, cmp> pq;
30     memset(dist, 0, sizeof(dist));
31     memset(flag, 0, sizeof(flag));
32     pq.push(P(0, 1));
33     while( !pq.empty() )
34     {
35         P t = pq.top();
36         pq.pop();
37         int v = t.second;
38         if(flag[v])
39             continue;
40         flag[v] = 1;
41         dist[v] = t.first;
42         for(int i = 1; i <= n; i++)
43         {
44             if(!flag[i])
45             {
46                 double m = max(dist[v], G[v][i]);
47                 pq.push(P(m, i));
48             }
49         }
50     }
51 
52 }
53 
54 
55 double calc(point a, point b)
56 {
57     double ans;
58     double x = a.x - b.x;
59     double y = a.y - b.y;
60     ans = sqrt(x*x + y*y);
61     return ans;
62 }
63 
64 
65 int main()
66 {
67     //freopen("in.txt", "r", stdin);
68     int Case = 1;
69     while(scanf("%d", &n) != EOF)
70     {
71         if(n == 0)
72             break;
73         if(Case != 1)
74             puts("");
75         for(int i = 1; i <= n; i++)
76         {
77             scanf("%d%d", &node[i].x, &node[i].y);
78         }
79         for(int i = 1; i <= n; i++)
80         {
81             for(int j = i+1; j <= n; j++)
82             {
83                 G[i][j] = calc(node[i], node[j]);
84                 G[j][i] = G[i][j];
85             }
86             G[i][i] = 0;
87         }
88         Dijkstra(1);
89         printf("Scenario #%d\n", Case++);
90         printf("Frog Distance = %.3f\n", dist[2]);
91     };
92     return 0;
93 }