POJ 1734 Sightseeing trip

题目大意：

求一个最小环。

用Floyd 求最小环算法。

#include <iostream>

#include <cstdlib>

#include <cstdio>

#include <algorithm>

#include <vector>

#include <queue>

#include <cmath>

#include <cstring>

using namespace std;

#define INF 0xfffffff

#define maxn 260



int G[maxn][maxn], dist[maxn][maxn];

int Pre[maxn][maxn], Path[maxn];

int m, n, CrossNum = 0;





void SearchPath(int Star,int End)

{

    while(Star != End)

    {

        Path[CrossNum ++] = Star;

        Star = Pre[Star][End];

    }

    Path[CrossNum ++] = Star;

}



void Floyd()

{

    int MinLoop = INF;

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

    {

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

        {

            for(int j=i+1; j<k; j++)

            {

                if( dist[i][j] + G[i][k] + G[k][j] < MinLoop )

                {

                    MinLoop =  dist[i][j] + G[i][k] + G[k][j];

                    CrossNum = 0;

                    SearchPath(i,j);

                    Path[CrossNum++] = k;

                }

            }

        }





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

        {

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

            {

                if(dist[i][j] > dist[i][k] + dist[k][j])

                {

                    dist[i][j] = dist[i][k] + dist[k][j];

                    Pre[i][j] = Pre[i][k];

                }

            }

        }

    }

}

void Init()

{

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

    {

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

        {

            dist[i][j] = G[i][j] = INF;

            Pre[i][j] = j;

            CrossNum = 0;

        }

    }

}





int main()

{

    while(cin >> n >> m)

    {





        Init();



        for(int i=0; i<m; i++)

        {

            int a, b, c;



            cin >> a >> b >> c;



            G[a][b] = G[b][a] = dist[a][b] = dist[b][a] = min(dist[a][b], c);

        }



        Floyd();



        if( CrossNum)

        {



            for(int i=0; i<CrossNum - 1; i++)

            {

                printf("%d ", Path[i]);

            }

            printf("%d\n", Path[CrossNum - 1]);

        }

        else

            cout <<"No solution." << endl;

    }

    return 0;

}