hdu 4318 Power transmission

http://acm.hdu.edu.cn/showproblem.php?pid=4318

很裸的spfa

#include<iostream>

#include<cstdio>

#include<algorithm>

#include<cstring>

#include<cmath>

#include<map>

#include<queue>

#include<cmath>

#define LL long long



using namespace std;



const int N=50040;

const double M=200000000.0;

struct node

{

    struct tt *next;

}mem[N];

struct tt

{

    struct tt *next;

    int j;

    int k;

};

void build(int i,int j,int k)

{

    struct tt *t=new tt;

    t->j=j;

    t->k=k;

    t->next=mem[i].next;

    mem[i].next=t;

}

void Dele(int n)

{

    for(int i=1;i<=n;++i)

    {

        mem[i].next=NULL;

    }

}

int n;

double dist[N];

void  spfa(int st,int nd,double power)

{

    for(int i=1;i<=n;++i)

    {

        if(i==st)

        dist[i]=power;

        else

        dist[i]=-1.0;

    }

    bool in[N];

    memset(in,false,sizeof(in));

    queue<int>str;

    in[st]=true;

    str.push(st);

    struct tt *t;

    while(!str.empty())

    {

        int x=str.front();

        in[x]=false;

        str.pop();

        t=mem[x].next;

        while(t!=NULL)

        {

            if(dist[x]*(t->k)/100.0>dist[t->j])

            {

                dist[t->j]=dist[x]*(t->k)/100.0;

                if(!in[t->j])

                {

                    in[t->j]=true;

                    str.push(t->j);

                }

            }

            t=t->next;

        }

    }

}

int main()

{

    //freopen("data.txt","r",stdin);

    while(scanf("%d",&n)!=EOF)

    {

        for(int i=1;i<=n;++i)

        {

            int j,k,w;

            scanf("%d",&w);

            while(w--)

            {

                scanf("%d %d",&j,&k);

                build(i,j,100-k);

            }

        }

        int st,nd;

        double power;

        scanf("%d %d %lf",&st,&nd,&power);

        if(st==nd)

        {

            printf("0.00\n");

            continue;

        }

        spfa(st,nd,power);

        if(dist[nd]<0.0)

        printf("IMPOSSIBLE!\n");

        else

        {

            printf("%.2lf\n",power-dist[nd]);

        }

        Dele(n);

    }

    return 0;

}