zoukankan      html  css  js  c++  java
  • HDU

    Travelling

    After coding so many days,Mr Acmer wants to have a good rest.So travelling is the best choice!He has decided to visit n cities(he insists on seeing all the cities!And he does not mind which city being his start station because superman can bring him to any city at first but only once.), and of course there are m roads here,following a fee as usual.But Mr Acmer gets bored so easily that he doesn't want to visit a city more than twice!And he is so mean that he wants to minimize the total fee!He is lazy you see.So he turns to you for help.

    InputThere are several test cases,the first line is two intergers n(1<=n<=10) and m,which means he needs to visit n cities and there are m roads he can choose,then m lines follow,each line will include three intergers a,b and c(1<=a,b<=n),means there is a road between a and b and the cost is of course c.Input to the End Of File.OutputOutput the minimum fee that he should pay,or -1 if he can't find such a route.Sample Input

    2 1
    1 2 100
    3 2
    1 2 40
    2 3 50
    3 3
    1 2 3
    1 3 4
    2 3 10

    Sample Output

    100
    90
    7 




    题意:每个点最多去两次,给出边权,求从任意一点开始经过所有点的最短路。

    经典TSP问题,只不过最多一次的条件变为两次,这里可以用三进制思想解决。
    three[n]表示n个地点的全部状态,0没去过,1去过一次,2去过两次,dig[i][j]记录在i状态下第j位的数字(0-2)。

    #include<bits/stdc++.h>
    #define MAX 12
    #define INF 0x3f3f3f3f
    using namespace std;
    typedef long long ll;
    
    int a[MAX][MAX];
    int three[MAX];
    int dig[60000][MAX];
    int dp[60000][MAX];
    
    void init(){
        three[0]=1;
        for(int i=1;i<=10;i++){
            three[i]=three[i-1]*3;
        }
        for(int i=0;i<three[10];i++){
            int ii=i,c=-1;
            while(ii){
                c++;
                dig[i][c]=ii%3;
                ii/=3;
            }
        }
    }
    int main()
    {
        int t,n,m,i,j,k;
        int x,y,z;
        init();
        while(~scanf("%d%d",&n,&m)){
            memset(a,INF,sizeof(a));
            for(i=0;i<m;i++){
                scanf("%d%d%d",&x,&y,&z);
                a[x][y]=a[y][x]=min(a[x][y],z);
            }
            memset(dp,INF,sizeof(dp));
            for(i=0;i<n;i++){
                dp[three[i]][i]=0;
            }
            for(i=0;i<three[n];i++){
                for(j=0;j<n;j++){
                    if(dig[i][j]==0) continue;
                    for(k=0;k<n;k++){
                        if(j==k||dig[i][k]==0) continue;
                        dp[i][j]=min(dp[i][j],dp[i-three[j]][k]+a[k+1][j+1]);
                    }
                }
            }
            int ans=INF;
            for(i=0;i<three[n];i++){
                int f=0;
                for(j=0;j<n;j++){
                    if(dig[i][j]==0){
                        f=1;
                        break;
                    }
                }
                if(f==1) continue;
                for(j=0;j<n;j++){
                    ans=min(ans,dp[i][j]);
                }
            }
            if(ans==INF) printf("-1
    ");
            else printf("%d
    ",ans);
        }
        return 0;
    }
  • 相关阅读:
    验证整数 Double 转 int 两种写法
    0 can't find referenced pointcut declarePointExpress
    nested exception is java.lang.IllegalArgumentException: Pointcut is not well-formed
    org.springframework.beans.factory.BeanDefinitionStoreException: Unexpected exception parsing XML doc
    嵌入式系统(胡威)2019年春第一次作业 参考答案
    PAT(B) 1021 个位数统计(Java)
    PAT(B) 1020 月饼(Java)
    PAT(B) 1019 数字黑洞(Java)
    PAT(B) 1018 锤子剪刀布(C:20分,Java:18分)
    PAT(B) 1017 A除以B(Java)
  • 原文地址:https://www.cnblogs.com/yzm10/p/9628834.html
Copyright © 2011-2022 走看看