21:49:45 2015-03-09
传送 http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1478
这题说的是运送货物需要交纳过路费。进入一个村庄需要交纳1个单位的货物，而进入一个城镇是每20个单位的货物中就要上缴1个单位的（70要上交4个）问选择哪条道路使得过路费最少，
这题我们知道了终太 ， 那么我们就可以逆推回去， 比如说我们知道了最后一站我们就可以逆推回上一站， 采用dijkstra 计算出每个点到终点的最优的过路费，再来一次贪心取最小的结果。
1 #include <iostream> 2 #include <algorithm> 3 #include <string.h> 4 #include <vector> 5 #include <queue> 6 #include <map> 7 #include <cstdio> 8 using namespace std; 9 const int maxn=100; 10 const long long INF = 1LL<<60; 11 typedef long long LL; 12 int hash_num(char c){ 13 if(c>='A'&&c<='Z') return c-'A'; 14 else return c-'a'+26; 15 } 16 char hash_char(int c){ 17 if(c>=0&&c<26) return c+'A'; 18 else return c-26+'a'; 19 } 20 int st,ed; 21 LL d[maxn]; 22 bool G[maxn][maxn],mark[maxn]; 23 LL projud(LL item, int next){ 24 if(next<26) return item-(item+19)/20; 25 return item-1; 26 } 27 LL jud(int u){ 28 if(u >= 26) return d[u]+1; 29 LL v = d[u]; 30 LL ans=0; 31 ans=v; 32 while(true){ 33 LL d=v/20; 34 v=v%20; 35 ans+=d; 36 v+=d; 37 if(d==0)break; 38 } 39 if(v) ans++; 40 return ans; 41 } 42 LL forward(LL item, int next) { 43 if(next < 26) return item - (item + 19) / 20; 44 return item - 1; 45 } 46 struct Head{ 47 LL d; int u; 48 bool operator < (const Head &r)const { 49 return d>r.d; 50 } 51 Head (LL dd =0, int uu = 0){ 52 d=dd; u = uu; 53 } 54 }; 55 void print(LL p){ 56 int nod=52; 57 memset(mark,false,sizeof(mark)); 58 for(int i =0; i<nod ; i++ )d[i]=INF; 59 d[ed]=p; 60 priority_queue<Head> Q; 61 Q.push(Head(p,ed)); 62 while(!Q.empty()){ 63 Head x= Q.top(); Q.pop(); 64 if(mark[x.u]) continue; 65 mark[x.u]=true; 66 for(int i=0; i<nod; ++i){ 67 LL pe = jud(x.u); 68 if(mark[i]==false&&G[i][x.u]&&pe<d[i]){ 69 d[i] = pe; 70 Q.push(Head(d[i],i)); 71 } 72 } 73 } 74 75 int u=st; 76 printf("%lld ",d[st]); 77 printf("%c",hash_char(u)); 78 79 LL item = d[st]; 80 while(u != ed ){ 81 int next; 82 for(next = 0; next < nod; next++) if(G[u][next] && forward(item, next) >= d[next]) break; 83 item = d[next]; 84 printf("-%c", hash_char(next)); 85 u = next; 86 } 87 printf(" "); 88 } 89 int main() 90 { 91 int n,cas=0; 92 char s1[9],s2[9]; 93 94 while(scanf("%d",&n)==1&&n!=-1){ 95 memset(G,false,sizeof(G)); 96 97 for(int i= 0; i<n; ++i){ 98 scanf("%s%s",s1,s2); 99 int u = hash_num(s1[0]); 100 int v = hash_num(s2[0]); 101 if(u==v)continue; 102 G[u][v]=G[v][u]=true; 103 104 105 } 106 LL p; 107 scanf("%lld%s%s",&p,s1,s2); 108 st = hash_num(s1[0]); ed = hash_num(s2[0]); 109 printf("Case %d: ",++cas); 110 print(p); 111 } 112 return 0; 113 }