TopCoder SRM194C: IslandFerries 题解

十分坑爹，题目中写的是“当你用完一张票到其他岛屿上时，你的手中只能有0,1,2张票，所以事实上任意时刻你的手上最多能有3张票
考虑状压dp
dp[i][Mask]表示当前在i号岛屿，现在手上有的票为Mask的最小代价
通过船票来进行转移即可

#include <cstdio>
#include <iostream>
#include <cstring>
#include <string>
#include <cstdlib>
#include <utility>
#include <cctype>
#include <algorithm>
#include <bitset>
#include <set>
#include <map>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <cmath>
#define LL long long
#define LB long double
#define x first
#define y second
#define Pair pair<int,int>
#define pb push_back
#define pf push_front
#define mp make_pair
#define LOWBIT(x) x & (-x)
using namespace std;

const int MOD=1e9+7;
const LL LINF=2e16;
const int INF=2e9;
const int magic=348;
const double eps=1e-10;
const double pi=3.14159265;

inline int getint()
{
    char ch;int res;bool f;
    while (!isdigit(ch=getchar()) && ch!='-') {}
    if (ch=='-') f=false,res=0; else f=true,res=ch-'0';
    while (isdigit(ch=getchar())) res=res*10+ch-'0';
    return f?res:-res;
}

class IslandFerries
{
    public:
        int price[48][48];Pair route[48][48];int num[48];
        int dp[48][1048];queue<int> q;bool inq[48][1048];
        int n,m;
        inline int STRING_TO_INT(string s)
        {
            int res=0,len=int(s.size()),i;
            for (i=0;i<=len-1;i++) res=res*10+s[i]-'0';
            return res;
        }
        inline void doit_price(int ind,string s)
        {
            s+=" ";
            int i,pos,pos1,len=int(s.size());
            for (i=1,pos=0;i<=m && pos<=len-1;i++,pos=pos1+1)
            {
                pos1=s.find(' ',pos);
                price[ind][i]=STRING_TO_INT(s.substr(pos,pos1-pos));
            }
        }
        inline void doit_leg(int ind,string s)
        {
            s+=" ";string ss;
            int i,pos,pos1,len=int(s.size()),pp1,pp2;
            num[ind]=0;
            for (i=1,pos=0;pos<=len-1;pos=pos1+1)
            {
                pos1=s.find(" ",pos);
                ss=s.substr(pos,pos1-pos);
                pp1=ss.find('-');
                route[ind][++num[ind]].x=STRING_TO_INT(ss.substr(0,pp1))+1;
                route[ind][num[ind]].y=STRING_TO_INT(ss.substr(pp1+1,int(ss.size())-pp1))+1;
            }
        }
        inline vector<int> costs(vector<string> legs,vector<string> prices)
        {
            int i,j,k,cur,Mask,to,toMask,cnt;
            m=int(legs.size());n=int(prices.size());
            for (i=1;i<=n;i++) doit_price(i,prices[i-1]);
            for (i=1;i<=m;i++) doit_leg(i,legs[i-1]);
            for (i=1;i<=n;i++)
                for (Mask=0;Mask<=(1<<m)-1;Mask++)
                    dp[i][Mask]=INF;
            dp[1][0]=0;q.push(1);q.push(0);
            memset(inq,false,sizeof(inq));inq[1][0]=true;
            while (!q.empty())
            {
                cur=q.front();q.pop();Mask=q.front();q.pop();inq[cur][Mask]=false;
                cnt=__builtin_popcount(Mask);
                for (i=1;i<=m;i++)
                    if (Mask&(1<<(i-1)))
                    {
                        for (j=1;j<=num[i];j++)
                            if (route[i][j].x==cur)
                            {
                                to=route[i][j].y;toMask=(Mask^(1<<(i-1)));
                                if (dp[to][toMask]>dp[cur][Mask])
                                {
                                    dp[to][toMask]=dp[cur][Mask];
                                    if (!inq[to][toMask]) inq[to][toMask]=true,q.push(to),q.push(toMask);
                                }
                            }
                    }
                    else
                    {
                        if (cnt>=3) continue;
                        to=cur;toMask=(Mask|(1<<(i-1)));
                        if (dp[to][toMask]>dp[cur][Mask]+price[cur][i])
                        {
                            dp[to][toMask]=dp[cur][Mask]+price[cur][i];
                            if (!inq[to][toMask]) inq[to][toMask]=true,q.push(to),q.push(toMask);
                        }
                    }
            }
            vector<int> res;
            for (i=2;i<=n;i++) if (dp[i][0]>=INF) res.pb(-1); else res.pb(dp[i][0]);
            return res;
        }
};

/*---Debug Part---*/
/*
int main ()
{
    int nn,mm;
    IslandFerries A;
    while (scanf("%d%d",&nn,&mm)!=EOF)
    {
        vector<string> aa,bb;
        int i;string s;getchar();
        for (i=1;i<=mm;i++) getline(cin,s),aa.pb(s);
        for (i=1;i<=nn;i++) getline(cin,s),bb.pb(s);
        vector<int> ans=A.costs(aa,bb);
        for (i=0;i<int(ans.size());i++) cout<<ans[i]<<endl;
    }
    return 0;