【HDU1301】Jungle Roads（MST基础题）

爽爆。史上个人最快MST的记录7分40s。。一次A。

 

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <cctype>
#include <algorithm>
#include <numeric>

#define typec int
using namespace std;

const typec inf = 0xffff;
const int V = 35;
int vis[V]; typec lowc[V];
int Map[V][V];

typec prim (typec cost[][V], int n) {
    int i, j, p;
    typec minc, res = 0;
    memset(vis, 0, sizeof (vis));
    vis[0] = 1;
    for (i = 1; i < n; ++ i) lowc[i] = cost[0][i];
    for (i = 1; i < n; ++ i) {
        minc = inf; p = -1;
        for (j = 0 ; j < n; ++ j) {
            if ( 0 == vis[j] && minc > lowc[j]) {
                minc = lowc[j]; p = j;
            }
        }
        if (inf == minc) return -1;
        res += minc; vis[p] = 1;
        for (j = 0 ; j < n; ++ j) {
            if (0 == vis[j] && lowc[j] > cost[p][j]) {
                lowc[j] = cost[p][j];
            }
        }
    }
    return res;
}


int main () {
    int n;
    while (~scanf("%d", &n)) {
        if (n == 0) break;
        for (int i = 0 ; i < n; ++ i) {
            for (int j = 0 ;j < n; ++ j) {
                if (i == j) Map[i][j] = 0;
                else Map[i][j] = inf;
            }
        }

        for (int i = 0 ; i < n - 1; ++ i) {
            char s_c; int e_n;
            cin >> s_c >> e_n;
            for (int j = 0 ; j < e_n; ++ j) {
                char e_c; int w;
                cin >> e_c >> w;
                Map[s_c - 'A'][e_c - 'A'] = Map[e_c - 'A'][s_c - 'A'] = min(Map[s_c - 'A'][e_c - 'A'], w);
            }
        }

        cout << prim(Map, n) << endl;
    }
    return 0;
}