poj 3225

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poj2449 削弱版本，于是在原来A∗基础上改改就A了。。。

但是这样不怎么好，于是我还是写了一个最短路算法。居然比原来慢。。。

#include<map>#include<queue>#include<stack>#include<utility>#include<string>#include<cstdio>#include<cstdlib>#include<cstring>#include<ctime>#include<cmath>#include<iostream>#include<algorithm>#define Mp(x,y) std::make_pair(x,y)#define Num second#define Min1 first#define Min2 second#define Dis first.first#define Tag first.secondconst int MAXN = 5e3+5, MAXM = 1e5+5, INF = 2e8;typedef std::pair<long long,long long> DistType;typedef std::pair<std::pair<long long,int>,int> HeapNode;typedef std::priority_queue<HeapNode,std::vector<HeapNode>,std::greater<HeapNode> > HeapType;struct Edge{int v,next;long long w; Edge(int v = 0,long long w = 0,int next = 0):v(v),w(w),next(next){}};int n, m;Edge edge[MAXM<<1];int el = 0, head[MAXN] = {0};HeapType line;bool flag[MAXN][2] = {false};DistType dist[MAXN];void NewEdge(int u,int v,long long w){++el; edge[el] = Edge(v,w,head[u]); head[u] = el;}void Dijstra(){    for(int i = 1; i <= n ; i++)       dist[i] = Mp(INF,INF);    dist[1] = Mp(0,INF);    line.push(Mp(Mp(0,0),1));    while(!line.empty())    {        HeapNode t = line.top();        line.pop();        if(flag[t.Num][t.Tag])continue;        flag[t.Num][t.Tag] = true;        for(int i = head[t.Num]; i ; i = edge[i].next)        {            int p = edge[i].v;            long long  tmp = t.Dis + edge[i].w;            if(tmp < dist[p].Min1)            {                dist[p].Min2 = dist[p].Min1;                dist[p].Min1 = tmp;                line.push(Mp(Mp(dist[p].Min1,0),p));                line.push(Mp(Mp(dist[p].Min2,1),p));            }            else if(tmp < dist[p].Min2)            {                dist[p].Min2 = tmp;                line.push(Mp(Mp(dist[p].Min2,1),p));            }            else;        }    }}int main(){#ifndef ONLINE_JUDGE    freopen("poj3255.in","r",stdin);    freopen("poj3255.out","w",stdout);#endif    std::cin >> n >> m;    for(int i = 1 , a, b, l; i <= m ; i++)    {        scanf("%d%d%d",&a,&b,&l);        NewEdge(a,b,l); NewEdge(b,a,l);    }    Dijstra();    std::cout << dist[n].Min2 << std::endl;    fprintf(stderr,"%f",clock()*1.0/CLOCKS_PER_SEC);#ifndef ONLINE_JUDGE    fclose(stdin);    fclose(stdout);#endif    return 0;}

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