HNU 11072 && PKU 3635 Full Tank？

优先队列广搜求最短路

Code for HNU 11072 
 1 /*
 2  * File:   PKU 3635 Full Tank?
 3  * Author: xiaotian @ hnu
 4  * Created on 2010年10月8日, 下午4:27
 5  * 题解：优先队列bfs
 6  */
 7 #include<iostream>
 8 #include<math.h>
 9 #include<queue>
10 #include<stdio.h>
11 #include<algorithm>
12 #include<string.h>
13 #include<vector>
14  using namespace std;
15  #define N 1008
16  #define inf 0x7fffffff
17 struct node {
18     int v, dist;
19     node(int a = 0, int b = 0) : v(a), dist(b) {
20     }
21 };
22 struct Node {
23     int v,rest,cost;
24     Node(int a = 0, int b = 0, int c = 0) : v(a), rest(b), cost(c) {
25     }
26     bool operator<(const Node &r) const{
27         return r.cost < cost;
28     }
29 };
30 vector<node>g[N];
31 int dp[N][102];
32 bool vist[N][102];
33 int n, m, a[N], V, S, T, ans;
34 priority_queue<Node>q;
35 int bfs() {
36     int x, y, z;
37     while (!q.empty())
38         q.pop();
39     q.push(Node(S, 0, 0));
40     dp[S][0] = 0;
41     while (!q.empty()) {
42         Node p = q.top();
43         q.pop();
44         x = p.v, y = p.rest, z = p.cost;
45         vist[x][y] = 1;
46         if (x == T) return z;
47         if (y + 1 <= V && !vist[x][y + 1] && dp[x][y + 1] > dp[x][y] + a[x]) {
48             dp[x][y + 1] = dp[x][y] + a[x];
49             q.push(Node(x, y + 1, dp[x][y + 1]));
50         }
51         for (int i = 0; i < g[x].size(); i++) {
52             int t = g[x][i].v;
53             int k = y - g[x][i].dist;
54             if (k >= 0 && !vist[t][k] && z < dp[t][k]) {
55                 dp[t][k] = z;
56                 q.push(Node(t, k, dp[t][k]));
57             }
58         }
59     }
60     return -1;
61 }
62 int main() {
63     int i, j;
64     while (scanf("%d%d", &n, &m) != EOF) {
65         for (i = 0; i < n; i++) {
66             scanf("%d", &a[i]);
67             g[i].clear();
68         }
69         int u, v, w;
70         for (i = 0; i < m; i++) {
71             scanf("%d%d%d", &u, &v, &w);
72             g[u].push_back(node(v, w));
73             g[v].push_back(node(u, w));
74         }
75         int tc;
76         scanf("%d", &tc);
77         while (tc--) {
78             scanf("%d%d%d", &V, &S, &T);
79             memset(vist, 0, sizeof (vist));
80             for (i = 0; i < n; i++)
81                 for (j = 0; j <= 100; j++)
82                     dp[i][j] = inf;
83             ans = bfs();
84             if (ans == -1)
85                 printf("impossible\n");
86             else
87                 printf("%d\n", ans);
88         }
89     }
90     return 0;
91 }
92

 

 

 

posted @ 2010-10-08 19:29  晓天  阅读(272)  评论(0)    收藏  举报