HDU6005 -dijkstra+剪枝

题有毒，题意是让你求一个最小权值的环。
思路：枚举每一条边然后每次跑一遍dij，再加上这条边的权值，就是结果了。
然后就TLE啦，那就剪枝，每次跑的时候如果遇到已经大于ans的结果是就直接break。

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#include <iostream>#include <cstring>#include <string>#include <algorithm>#include <cstdio>#include <cmath>#include <map>#include <set>#include <queue>#include <vector>#define mod  1000000007#define INF  0x3f3f3f3f#define fuck() (cout << "----------------------------------------" << endl)using namespace std;const int maxn = 10000 + 5;typedef pair<int,int> P;map<P,int> num;vector <P> vec[maxn];int n,cnt,ans;bool vis[maxn];int dis[maxn];struct EDGE{    int u;    int v;    int w;    EDGE(){}    EDGE(int a, int b, int c)    {        u = a , v = b, w = c;    }};EDGE edge[maxn];void dij(int source, int end, int cost){    for(int i=0; i<maxn; i++)    {        vis[i] = false;        dis[i] = INF;    }    dis[source] = 0;    priority_queue<P,vector<P>,greater<P> > q;    q.push(make_pair(0,source));    while(!q.empty())    {        P p = q.top();        q.pop();        int u = p.second, d = p.first;        if(d + cost >= ans) break;        if(vis[u]) continue;        vis[u] = true;        for(int i=0; i<vec[u].size(); i++)        {            P temp = vec[u][i];            int v = temp.first;            int fck = temp.second;            EDGE e = edge[fck];            int c = e.w;            if(dis[v] > dis[u] + c)            {                dis[v] = dis[u] + c;                q.push(make_pair(dis[v],v));            }        }    }    ans = min(ans, dis[end] + cost);}int main(){    int T, kases = 1;    scanf("%d",&T);    while(T--)    {        for(int i=0; i<maxn; i++)            vec[i].clear();        num.clear();        scanf("%d",&n);        cnt = 0;        for(int i=0; i<n; i++)        {            int x1,y1,x2,y2,w;            scanf("%d%d%d%d%d",&x1,&y1,&x2,&y2,&w);            P p1 = make_pair(x1,y1);            P p2 = make_pair(x2,y2);            if(!num.count(p1)) num[p1] = cnt++;            if(!num.count(p2)) num[p2] = cnt++;            int num1 = num[p1], num2 = num[p2];            vec[num1].push_back(make_pair(num2,i));            vec[num2].push_back(make_pair(num1,i));            edge[i] = EDGE(num1,num2,w);        }        ans = INF;        for(int i=0; i<n; i++)        {            int u = edge[i].u, v = edge[i].v, w = edge[i].w;            edge[i].w = INF;            dij(u,v,w);            edge[i].w = w;        }        if(ans == INF) ans = 0;        printf("Case #%d: %d\n",kases++,ans);    }}