题意：最短路上有一条高度限制，给起点和最大高度，求满足高度最大情况下，最短路的距离
不明白为什么枚举所有高度就不对
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 const int maxint=999999; 5 int c[1005][1005][2],dist[1005],H[1005]; 6 using namespace std; 7 int n,line; 8 int i,j,k; 9 int st,ed,mid; 10 int t=0; 11 int path[1005]; 12 int visit[1005]; 13 bool dijkstra() 14 { 15 bool s[1005]; 16 for(int i=1;i<=n;i++) 17 { 18 s[i]=0; 19 if(c[st][i][0]>=mid) 20 dist[i]=c[st][i][1]; 21 else dist[i]=maxint; 22 path[i]=st; 23 } 24 s[st]=1; 25 for(int i=1;i<n;i++) 26 { 27 int temp=maxint; 28 int u=st; 29 for(int j=1;j<=n;j++) 30 if(!s[j]&&temp>dist[j]&&c[path[j]][j][0]>=mid) 31 { 32 temp=dist[j]; 33 u=j; 34 } 35 if(temp==maxint) break; 36 s[u]=1; 37 if(u==ed) return true; 38 for(int j=1;j<=n;j++) 39 if(!s[j]&&c[u][j][1]!=maxint&&c[u][j][0]>=mid) 40 if(dist[j]>dist[u]+c[u][j][1]) 41 { 42 dist[j]=dist[u]+c[u][j][1]; 43 path[j]=u; 44 } 45 } 46 return false; 47 } 48 int main() 49 { 50 #ifndef ONLINE_JUDGE 51 freopen("1.in","r",stdin); 52 #endif 53 while(scanf("%d%d",&n,&line)!=EOF&&n&&line) 54 { 55 int tot=1; 56 memset(H,0,sizeof(H)); 57 H[0]=0; 58 if(t) printf(" "); 59 printf("Case %d: ",++t); 60 for(i=1;i<=n;i++) 61 for(j=1;j<=n;j++) 62 { 63 c[i][j][1]=(i==j?0:maxint); 64 c[i][j][0]=-999999; 65 } 66 for(i=1;i<=line;i++) 67 { 68 int p,q,len,h; 69 scanf("%d%d%d%d",&q,&p,&h,&len); 70 if(h==-1) 71 { 72 c[p][q][0]=c[q][p][0]=maxint; 73 c[p][q][1]=c[q][p][1]=len; 74 continue; 75 } 76 if(c[p][q][0]<h) 77 { 78 c[p][q][0]=c[q][p][0]=h; 79 c[p][q][1]=c[q][p][1]=len; 80 } 81 } 82 int tall; 83 scanf("%d%d%d",&st,&ed,&tall); 84 /*if(st==ed) 85 { 86 printf("maximum height = %d ",tall); 87 printf("length of shortest route = 0 "); 88 continue; 89 }*/ 90 /*H[tot++]=tall; 91 sort(H,H+tot); 92 int ans=0; 93 bool flag=0; 94 for(i=tot-1;i>=0;i--) 95 { 96 if(H[i]>tall) continue; 97 mid=H[i]; 98 if(dijkstra()) 99 { 100 flag=1; 101 ans=dist[ed]; 102 break; 103 } 104 }*/ 105 int first=1; 106 int ans; 107 mid=(first+tall)>>1; 108 while(first<=tall) 109 { 110 if(dijkstra()) 111 { 112 ans=dist[ed]; 113 first=mid+1; 114 } 115 else 116 tall=mid-1; 117 mid=(first+tall)>>1; 118 } 119 if(tall==0) printf("cannot reach destination "); 120 else 121 { 122 printf("maximum height = %d ",tall); 123 printf("length of shortest route = %d ",ans); 124 } 125 } 126 return 0; 127 }