Lost in Translation

题目链接：http://acm.hunnu.edu.cn/online/?action=problem&type=show&id=11739

贪心思想，建立分层图，对于层次不同的结点，层次靠近源点的在前面，对于层次相同的结点，费用小的放前面

直接用priority_queue建立一个有层次的堆，然后不断更新费用

#include <cstdio>#include <cstring>#include <map>#include <queue>#include <string>#include <iostream>#include <algorithm>using namespace std;typedef long long llt;struct edge_t{    int v,next;    llt cost;    edge_t(int a=0,llt b=0) {v=a;cost=b;}}edge[10000];int vertex[320];int Ecnt;struct qnode{    int v,heaps;    llt cost;    qnode(int _v=0,int _heaps=0,llt _cost=0) {v=_v;heaps=_heaps;cost=_cost;}    bool operator < (const qnode &r)const    {        if(heaps!=r.heaps) return heaps>r.heaps;        return cost>r.cost;    }};void init_Graph(){    Ecnt=1;    memset(vertex,0,sizeof(vertex));}void Build_edge(int a,int b,llt c){    edge[Ecnt].v=b;    edge[Ecnt].cost=c;    edge[Ecnt].next=vertex[a];    vertex[a]=Ecnt++;}bool vis[320];void bfs(int s,int n){    llt fee=0;    int cnt=0;    memset(vis,false,sizeof(vis));    priority_queue<qnode> q;    while(!q.empty()) q.pop();    qnode tmp(0,0,0);    q.push(tmp);    while(!q.empty())    {        tmp=q.top();        q.pop();        int u=tmp.v;        int h=tmp.heaps;        if(vis[u]) continue;        vis[u]=true;        //printf("Have vis %d\n",u);        fee+=tmp.cost;        cnt++;        if(cnt==n+1) break;        for(int next=vertex[u];next;next=edge[next].next)        {            int to=edge[next].v,cost=edge[next].cost;            q.push(qnode(to,h+1,cost));        }    }    if(cnt==n+1) printf("%I64d\n",fee);    else printf("Impossible\n");}map<string,int> lau;int main(){    int n,m;    string tmp;    string a,b;    while(scanf("%d%d",&n,&m)!=EOF)    {        init_Graph();        lau.clear();        llt fee;        lau.insert(make_pair("English",0));        for(int i=1;i<=n;i++)        {            cin>>tmp;            lau.insert(make_pair(tmp,i));        }        for(int i=1;i<=m;i++)        {            cin>>a>>b>>fee;            Build_edge(lau[a],lau[b],fee);            Build_edge(lau[b],lau[a],fee);        }        bfs(0,n);    }    return 0;}