HDU1301(最小生成树)

大意：给定一个图，求能连接所有点的最少权值和。

分析：最小生成树Prim算法。

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
const int INF = 1 << 30;
int map[27][27];//map存图
int d[27];//记录每2个点间的最小权值
bool visit[27];//记录点是否访问
int main()
{
	int  m, n, minn, temp, sum;
	char ch;
	//freopen("F:in.txt", "r", stdin);
	while (~scanf("%d", &n) && n)
	{
		memset(map,0x1f,sizeof(map));
		memset(d, 0, sizeof(d));
		memset(visit, 1, sizeof(visit));
		for (int i = 1; i < n; i++)
		{
			getchar();
			scanf("%c", &ch);
			scanf("%d", &m);
			for (int j = 1; j <= m; j++)
			{
				scanf("%c", &ch);
				scanf("%c", &ch);
				scanf("%d", &temp);
				map[i - 1][ch - 'A'] = temp;
				map[ch - 'A'][i - 1] = temp;
			}
		}
		for (int i = 1; i < n; i++)
			d[i] = map[i][0];//初始化第一个点到剩下点的距离
		sum = 0;
		visit[0] = 0;
		for (int i = 1; i < n; i++)
		{
			minn = INF;
			for(int j=0;j<n;j++)
				if (visit[j] && d[j] < minn)
				{
					minn = d[j];
					temp = j;
				}////找出最小权值并记录位置
			visit[temp] = 0;
			sum += minn;
			for (int j = 0; j < n; j++)
			{
				if (visit[j] && d[j] > map[j][temp])//更新权值
					d[j] = map[j][temp];
			}
		}
		printf("%d\n", sum);
	}
	return 0;
}