POJ 2449 Remmarguts' Date K短路

Remmarguts' Date Time Limit: 4000MS   Memory Limit: 65536K Total Submissions: 21013   Accepted: 5717 Description "Good man never makes girls wait or breaks an appointment!" said the mandarin duck father. Softly touching his little ducks' head, he told them a story.  "Prince Remmarguts lives in his kingdom UDF – United Delta of Freedom. One day their neighboring country sent them Princess Uyuw on a diplomatic mission."  "Erenow, the princess sent Remmarguts a letter, informing him that she would come to the hall and hold commercial talks with UDF if and only if the prince go and meet her via the K-th shortest path. (in fact, Uyuw does not want to come at all)"  Being interested in the trade development and such a lovely girl, Prince Remmarguts really became enamored. He needs you - the prime minister's help!  DETAILS: UDF's capital consists of N stations. The hall is numbered S, while the station numbered T denotes prince' current place. M muddy directed sideways connect some of the stations. Remmarguts' path to welcome the princess might include the same station twice or more than twice, even it is the station with number S or T. Different paths with same length will be considered disparate.  Input The first line contains two integer numbers N and M (1 <= N <= 1000, 0 <= M <= 100000). Stations are numbered from 1 to N. Each of the following M lines contains three integer numbers A, B and T (1 <= A, B <= N, 1 <= T <= 100). It shows that there is a directed sideway from A-th station to B-th station with time T.  The last line consists of three integer numbers S, T and K (1 <= S, T <= N, 1 <= K <= 1000). Output A single line consisting of a single integer number: the length (time required) to welcome Princess Uyuw using the K-th shortest path. If K-th shortest path does not exist, you should output "-1" (without quotes) instead. Sample Input 2 2 1 2 5 2 1 4 1 2 2 Sample Output 14 Source POJ Monthly,Zeyuan Zhu

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spfa+A*算法模板题

#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <vector>
#include <string>
#include <iostream>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <fstream>
#include <numeric>
#include <iomanip>
#include <bitset>
#include <list>
#include <stdexcept>
#include <functional>
#include <utility>
#include <ctime>

using namespace std;

#define PB push_back
#define MP make_pair
#define CLR(vis) memset(vis,0,sizeof(vis))
#define MST(vis,pos) memset(vis,pos,sizeof(vis))
#define MAX3(a,b,c) max(a,max(b,c))
#define MAX4(a,b,c,d) max(max(a,b),max(c,d))
#define MIN3(a,b,c) min(a,min(b,c))
#define MIN4(a,b,c,d) min(min(a,b),min(c,d))
#define PI acos(-1.0)
#define INF 1000000000
#define LINF 1000000000000000000LL
#define eps 1e-8

typedef long long ll;
typedef unsigned long long ull;

const int N=1000+10;
const int M=100000+10;

int n,m;
int s,t,k;
int dis[N],vis[N];

vector< pair<int,int> > e[M];
vector< pair<int,int> > re[M];

struct edge
{
    int v;
    int w;
    friend bool operator<(edge a,edge b)
    {
        return (a.w+dis[a.v])>(b.w+dis[b.v]);
    }
};

void init()
{
    for(int i=0;i<N;i++)
        e[i].clear(),re[i].clear();
}

void spfa(int s)
{
    CLR(vis);
    for(int i=0;i<N;i++)
        dis[i]=INF;
    dis[s]=0;
    vis[s]=1;
    queue<int> q;
    q.push(s);
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=0;i<re[u].size();i++)
        {
            int v=re[u][i].first,w=re[u][i].second;
            if(dis[v]>dis[u]+w)
            {
                dis[v]=dis[u]+w;
                if(!vis[v])
                {
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
}

int a_star()
{
    if(s==t)
        k++;
    if(dis[s]==INF)
        return -1;
    int v,w,cnt[N];
    edge n1,n2;
    priority_queue<edge> q;
    CLR(cnt);
    n1.v=s;
    n1.w=0;
    q.push(n1);
    while(!q.empty())
    {
        n2=q.top();
        q.pop();
        v=n2.v;
        w=n2.w;
        cnt[v]++;
        if(cnt[t]==k)
            return w;
        if(cnt[v]>k)
            continue;
        for(int i=0;i<e[v].size();i++)
        {
            n1.v=e[v][i].first;
            n1.w=w+e[v][i].second;
            q.push(n1);
        }
    }
    return -1;
}


int main()
{
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        init();
        int u,v,w;
        for(int i=0;i<m;i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            e[u].PB( MP(v,w) );
            re[v].PB( MP(u,w));
        }
        scanf("%d%d%d",&s,&t,&k);
        spfa(t);
        int ans=a_star();
        printf("%d\n",ans);
    }
    return 0;
}