2015年清华计算机考研复试 机试试题4

思路：

将所有的边按照降序排列，从大到小逐一挑选边，当已经挑选的边组成的连通分支中，最大的一个连通分支含有k个顶点，则算法终止。

代码：

#include<iostream>
#include<algorithm>
using namespace std;

struct Arc
{
	int from;
	int to;
	int weight;
};
bool cmp(const Arc& A, const Arc& B)
{
	return A.weight > B.weight;
}
int main()
{
	int **G;
	int *groupId;
	Arc *arc;
	int n, m, k;
	while(cin >> n >> m >> k)
	{
		//创建及初始化数组
		arc = new Arc[m];
		G = new int*[n];
		groupId = new int[n];
		for(int i = 0; i < n; i++)
		{
			G[i] = new int[n];
			groupId[i] = i;
		}
		//读取数据
		int from, to, weight;
		for(int i = 0; i < m; i++)
		{
			cin >> from >> to >> weight;
			G[from - 1][to - 1] = weight;
			arc[i].from = from - 1;
			arc[i].to = to - 1;
			arc[i].weight = weight;
		}
		//排序
		sort(arc, arc + m, cmp);
		
		/*
		//debug
		for(int i = 0; i < m; i++)
			cout << arc[i].from << ' ' << arc[i].to << ' ' << arc[i].weight << endl;
		system("pause");
		*/

		//从大到小逐一挑选边
		int maxGroup;
		int maxWeight = 0;
		for(int i = 0; i < m; i++)
		{
			maxGroup = 0;
			int id = groupId[arc[i].to];
			for(int j = 0; j < n; j++)
			{
				if(groupId[j] == id)
				{
					groupId[j] = groupId[arc[i].from];
					maxGroup++;
				}
				else if(groupId[j] == groupId[arc[i].from])
					maxGroup++;
			}
			if(maxGroup >= k)
			{
				maxWeight = arc[i].weight;
				break;
			}
		}

		//输出
		cout << maxWeight << endl;

		//析构数组
		for(int i = 0; i < n; i++)
			delete[] G[i];
		delete[] G;
		delete[] arc;
		delete[] groupId;
	}


    //system("pause");
    return 0;
}