poj 2253 dijkstra模板的使用

需要对于模板进行修改

题意:给定N个点,求从1到2的所有路径中最大边长最小的解(最大值最小)

依据dijkstra单源最短路径的贪心思想

d[i] 表示从源点s到i所满足条件的值

那么 d[i] = min { max(d[k], e(k to i) ) } 

松弛的时候

        if d[i] > max(d[cur], edge)

d[i] = max(d[cur], edge)

注意数据类型int和double切换

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

///宏定义
const int  INF = 10000000;
const int MAXN = 310;
const int maxn = MAXN;
///全局变量 和 函数
///


struct Edge
{
	int from;
	int to;
	double dist;
};
struct HeapNode
{
	int u;
	double d;
	bool operator < (const HeapNode& rhs) const
	{
		return d > rhs.d;
	}
};
struct Dijkstra
{
	int n, m;             //点数和边数
	vector edges;   //边列表
	vector G[maxn];  //每个结点出发的边编号
	bool done[maxn];      //是否已永久编号
//	int d[maxn];          //s到各个点的距离
	double d[maxn];
	int p[maxn];          //最短路中的上一条边 (打印结果用)

	void init(int n)
	{
		this->n = n;
		for (int i = 0; i <= n; i++)
			G[i].clear();
		edges.clear();
	}

	void AddEdge(int from, int to, double dist)
	{
		Edge tmp;
		tmp.from = from;
		tmp.to = to;
		tmp.dist = dist;
		edges.push_back(tmp);
		m = edges.size();
		G[from].push_back(m - 1);
	}

	void dijkstra(int s)
	{
		priority_queue Q;
		for (int i = 0; i <= n; i++)
			d[i] = INF;
		d[s] = 0;
		memset(done, 0, sizeof(done));
		HeapNode tmp;
		tmp.d = 0;
		tmp.u = s;
		Q.push(tmp);
		while (!Q.empty())
		{
			HeapNode x = Q.top();
			Q.pop();
			int u = x.u;
			if (done[u])
				continue;
			done[u] = true;
			for (int i = 0; i < G[u].size(); i++)
			{
				Edge &e = edges[G[u][i]];
				if (d[e.to] > max(d[u], e.dist))
				{
					d[e.to] = max(d[u], e.dist);
//					p[e.to] = G[u][i];
					HeapNode temp;
					temp.d = d[e.to];
					temp.u = e.to;
					Q.push(temp);
				}
			}
		}
	}
};
int n;
double posx[maxn];
double posy[maxn];
int main()
{

	///变量定义
	int i, j;
	int cases = 1;
	while (1)
	{
		scanf("%d", &n);
		if (n == 0)
			break;
		Dijkstra dij;
		dij.init(n);
		for (i = 1; i <= n; i++)
		{
			cin >> posx[i] >> posy[i];
		}
		for (i = 1; i <= n; i++)
		{
			for (j = 1; j <= n; j++)
			{
				if (i != j)
				{
					double dist = sqrt( (posx[i] - posx[j]) * (posx[i] - posx[j]) + (posy[i] - posy[j]) * (posy[i] - posy[j]) );
					dij.AddEdge(i, j, dist);
//					dij.AddEdge(j, i, dist);
				}
			}
		}
		dij.dijkstra(1);
		double ans = dij.d[2];
		printf("Scenario #%d\n", cases++);
		printf("Frog Distance = %.3f\n", ans);
		printf("\n");
	}



	///结束
	return 0;
}


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