HDU 1690 Bus System (最短路径bellmamford算法)

把题目理解后就可以构造图，形成求解最短路径，可以bellmanford算法求单元最短路径，当然也可以用floyd算法求点对的最短路径，但是相比起来，floyd更快一点吧！ke可能是因为给的测试数据更多点额是点对的求最短路径！！

同时要注意要用long long型，不然就挂惨喽！

下面是代码，给出的事Bellmanford算法，Floyd比较容易实现！

#include<iostream>#include<cstdlib>#include<stdio.h>#include<math.h>using namespace std;const long long inf=0x7f7f7f7f7f7f7f7fLL,Max=106;long long Map[Max][Max],d[Max],p[Max];long long l[5],c[5];long long bellmanford(int n,int s,int e){int i,j,k,index;for(i=1;i<=n;i++)d[i]=inf;d[s]=0;for(k=1;k<n;k++){index=0;for(i=1;i<=n;i++){for(j=1;j<=n;j++){if(Map[i][j]<inf&&d[i]<inf){if(d[j]>Map[i][j]+d[i]){d[j]=Map[i][j]+d[i];index=1;}}}}if(index==0)break;}return d[e];}int main(){int T,n,m,i,j,cas,s,e;long long dis,ans;scanf("%d",&T);for(cas=1;cas<=T;cas++){for(i=1;i<=4;i++)scanf("%I64d",&l[i]);for(i=1;i<=4;i++)scanf("%I64d",&c[i]);scanf("%d%d",&n,&m);for(i=1;i<=n;i++)for(j=1;j<=n;j++){if(i==j)Map[i][j]=0;elseMap[i][j]=inf;}for(i=1;i<=n;i++){scanf("%I64d",&p[i]);for(j=1;j<i;j++){dis=abs(p[i]-p[j]);if(0<dis&&dis<=l[1])Map[i][j]=Map[j][i]=c[1];if(dis>l[1]&&dis<=l[2])Map[i][j]=Map[j][i]=c[2];if(dis>l[2]&&dis<=l[3])Map[i][j]=Map[j][i]=c[3];if(dis>l[3]&&dis<=l[4])Map[i][j]=Map[j][i]=c[4];}}printf("Case %d:/n",cas);while(m--){scanf("%d%d",&s,&e);ans=bellmanford(n,s,e);if(ans<inf)printf("The minimum cost between station %d and station %d is %I64d./n",s,e,ans);elseprintf("Station %d and station %d are not attainable./n",s,e);}}}

最近进步很大，不过又有些颓废了，还是要继续加油啊！

杭电的最短路径都快被我切圆了，继续加油吧！！！