POJ 1502 MPI Maelstrom(Dijkstra)

POJ 1502 MPI Maelstrom(Dijkstra)

http://poj.org/problem?id=1502

题意: (整个第一段题意描述都是无关的话,可以直接看input)题目的输入给了你一个n个节点的无向图的邻接矩阵的下三角部分.要求你输出从第0个点到所有其他点的距离的最大值.

分析:

Dijkstra入门题,直接用刘汝佳的模板处理即可.

AC代码:

#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
const int maxn = 100+5;
#define INF 1e8
int n;
struct Edge
{
    int from,to,dist;
    Edge(){}
    Edge(int f,int t,int d):from(f),to(t),dist(d){}
};

struct HeapNode
{
    int d,u;
    HeapNode(){}
    HeapNode(int d,int u):d(d),u(u){}
    bool operator < (const HeapNode &rhs)const
    {
        return d > rhs.d;
    }
};

struct Dijkstra
{
    int n,m;
    vector<Edge> edges;
    vector<int> G[maxn];
    bool done[maxn];
    int d[maxn];
    int p[maxn];

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

    void dijkstra(int s)
    {
        priority_queue<HeapNode> Q;
        for(int i=0;i<n;i++) d[i]=INF;
        d[s]=0;
        memset(done,0,sizeof(done));
        Q.push(HeapNode(0,s) );

        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]> d[u]+e.dist)
                {
                    d[e.to] = d[u]+e.dist;
                    p[e.to] = G[u][i];
                    Q.push(HeapNode(d[e.to],e.to) );
                }
            }
        }
    }
}DJ;

int main()
{
    while(scanf("%d",&n)==1)
    {
        DJ.init(n);
        for(int i=1;i<n;i++)
        for(int j=0;j<i;j++)
        {
            char str[10];
            int d;
            scanf("%s",str);
            if(str[0]!='x')
            {
                sscanf(str,"%d",&d);
                DJ.AddEdge(i,j,d);
                DJ.AddEdge(j,i,d);
            }
        }
        DJ.dijkstra(0);
        int max_v=-1;
        for(int i=0;i<n;i++)
            max_v = max(max_v,DJ.d[i]);
        printf("%d\n",max_v);
    }
    return 0;
}