poj 1251 Jungle Roads（最小生成树，普里姆算法）

小记：题目都没看清，直接看样例做的，然后输入n以为就有n行，然后样例都没过，改成输入n-1行，直接prim带过

思路：注意路上无向路，处理的时候我直接是读字符串，然后去第一个字符，这样方便多了

算法就是prim

代码：

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <string>

using namespace std;

#define mst(a,b) memset(a,b,sizeof(a))
#define REP(a,b,c) for(int a = b; a < c; ++a)
#define eps 10e-8

const int MAX_ = 155;
const int N = 100010;
const int INF = 0x7fffffff;

int n;

struct node{
    int s, t;
};

int g[MAX_][MAX_];
int d[MAX_];
bool vis[MAX_];
int m, cnt;

int prim(int start)
{
    REP(i, 0, n){
        d[i] = INF;
        vis[i] = 0;
    }
    int sum = 0;
    d[start] = 0;

    REP(i, 0, n){
        int mmin = INF, k;
        REP(j, 0, n){
            if(!vis[j] && d[j] < mmin){
                mmin = d[j];
                k = j;
            }
        }
        if(mmin == INF)break;
        vis[k]  = 1;
        sum += mmin;
        REP(j, 0, n){
            if(!vis[j]  && g[k][j] != -1 && d[j] > g[k][j]){
                d[j] = g[k][j];
            }
        }
    }
    return sum;
}




int main(){
	int T, ss, tt;
	char str[10];

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

        mst(g, -1);

        REP(i, 0, n-1){
            scanf("%s", str);
            ss = str[0] - 'A';
            scanf("%d", &m);
            REP(j, 0, m){
                scanf("%s%d",str,&tt);
                g[ss][str[0]-'A'] = g[str[0] - 'A'][ss] = tt;
            }
        }
/*
        REP(i, 0, n)REP(j, 0, n){
            printf("%d ", g[i][j]);
            if(j == n-1)printf("\n");
        }*/

        int ans = prim(0);

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

	}
	return 0;
}