POJ 1251 Jungle Roads

先将字母转换成数字，然后建图。建完图用堆优化的prim，写这道

题花了不少时间，居然写成了dij，搞混了。

/*Accepted    180K    0MS    C++    1594B    2012-07-27 15:57:47*/

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<queue>

#include<iostream>

using namespace std;



const int MAXN = 1 << 5;

const int inf = 0x3f3f3f3f;

bool vis[MAXN];

int g[MAXN][MAXN], n;



int pos( char c)

{

    return c - 'A';

}



void ReadGraph()

{

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

        for( int j = 0; j < n; j ++)

        {

            if( i != j)

                g[i][j] = inf;

            else

                g[i][j] = 0;

        }

    int m, val;

    char a[5], b[5];

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

    {

        scanf( "%s%d", a, &m);

        while( m --)

        {

            scanf( "%s%d", b, &val);

            g[pos(a[0])][pos(b[0])] = g[pos(b[0])][pos(a[0])] = val;

        }

    }

}



int prim()

{

    int ret = 0, lowc[MAXN] = {0};

    typedef pair<int, int> pii;

    memset( vis, false, sizeof vis);

    priority_queue< pii, vector<pii>, greater<pii> > q;

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

        lowc[i] = inf;

    q.push( make_pair(lowc[0], 0));

    while( !q.empty())

    {

        pii u = q.top();q.pop();

        int x = u.second;

        if(vis[x]) continue;

        ret += lowc[x];

        vis[x] = true;

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

        {

            if( !vis[i] && g[x][i] < lowc[i])

            {

                lowc[i] = g[x][i];

                q.push( make_pair(lowc[i], i));

            }

        }

    }

    return ret;

}



int main()

{

    while( scanf( "%d", &n), n)

    {

        ReadGraph();

        printf( "%d\n", prim());

    }

    return 0;

}