标签:style blog http java color os
1 /* 2 题意:给出n个地点,每个地点的油价为pi每单位,给出m条边,每条长度为d,行走d距离的路需 3 要d单位的油;给出一辆车的油箱容量以及起始点:s,e;问s到e最少要耗费多少钱 4 5 题解:BFS+优先队列 6 这个搜索方式比较巧妙:状态为对于当前点是走还是油+1,这样就算想到了一般人也不太敢做, 7 毕竟看起来复杂度还是蛮高的;其中加了一个优先队列,作用是通过类似dijkstra的贪心的方法 8 保证求出的是最值,通过vis[][]记录状态即可去除重复。 9 */ 10 #include <cstdio> 11 #include <cstring> 12 #include <queue> 13 14 using namespace std; 15 16 const int MAXV = 1005; 17 const int MAXE = 30005; 18 19 struct edge 20 { 21 int v,w,next; 22 }E[MAXE]; 23 24 int EN; 25 int head[MAXV]; 26 27 void insert(int u, int v, int w) 28 { 29 E[EN].v = v; 30 E[EN].w = w; 31 E[EN].next = head[u]; 32 head[u] = EN++; 33 E[EN].v = u; 34 E[EN].w = w; 35 E[EN].next = head[v]; 36 head[v] = EN++; 37 } 38 39 int p[MAXV]; 40 41 struct node 42 { 43 int cost,v,oil; 44 bool operator<(const node &t)const 45 { 46 return cost > t.cost; 47 } 48 }; 49 50 bool vis[105][MAXV]; 51 52 int bfs(int c, int s, int e) 53 { 54 memset(vis,false,sizeof(vis)); 55 priority_queue<node> Q; 56 node start; 57 start.cost = 0; 58 start.oil = 0; 59 start.v = s; 60 Q.push(start); 61 while (!Q.empty()) 62 { 63 node now = Q.top(); 64 Q.pop(); 65 if (now.v == e) 66 return now.cost; 67 68 vis[now.oil][now.v] = true; 69 70 if (now.oil < c && !vis[now.oil+1][now.v]) 71 { 72 now.oil++; 73 now.cost += p[now.v]; 74 Q.push(now); 75 now.oil--; 76 now.cost -= p[now.v]; 77 } 78 79 for(int i=head[now.v]; i!=-1; i=E[i].next) 80 { 81 if (now.oil >= E[i].w && !vis[now.oil-E[i].w][E[i].v]) 82 { 83 node tmp = now; 84 tmp.oil -= E[i].w; 85 tmp.v = E[i].v; 86 Q.push(tmp); 87 } 88 } 89 } 90 return -1; 91 } 92 93 int main(void) 94 { 95 int n,m; 96 while (~scanf("%d%d",&n,&m)) 97 { 98 EN = 0; 99 memset(head,-1,sizeof(head)); 100 for(int i=0; i<n; i++) 101 scanf("%d",&p[i]); 102 for(int i=0; i<m; i++) 103 { 104 int u,v,d; 105 scanf("%d%d%d",&u,&v,&d); 106 insert(u,v,d); 107 } 108 109 int q; 110 scanf("%d",&q); 111 while (q--) 112 { 113 int s,e,c; 114 scanf("%d%d%d",&c,&s,&e); 115 int ans = bfs(c,s,e); 116 if (ans < 0) 117 printf("impossible\n"); 118 else 119 printf("%d\n",ans); 120 } 121 } 122 return 0; 123 }
poj 3635 BFS+优先队列,码迷,mamicode.com
标签:style blog http java color os
原文地址:http://www.cnblogs.com/toufu/p/3700330.html