hdu5876 Sparse Graph（补图最短路 bfs）

题目链接：hdu5876 Sparse Graph

详见代码。。

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<queue>
 #include<vector>
 #include<set>
 using namespace std;
 const int N = ;
 const int inf = 0x3f3f3f3f;
 int n, m;
 vector<vector<int> >g;
 int d[N];
 void bfs(int s){
     int u,v,i,j;
     queue<int>q;
     set<int>a; //不邻接的点
     set<int>b; //未扩展的点
     set<int>::iterator it;
     for(i = ; i <= n; ++i)
         a.insert(i);
     a.erase(s);
     q.push(s);
     while(!q.empty()){
         u=q.front();
         q.pop();
         for(j=;j<g[u].size();++j){
             v=g[u][j];
             if(!a.count(v))
                 continue;
             b.insert(v);
             a.erase(v);
         }
         for(it = a.begin(); it != a.end(); it++){
             d[*it] = d[u] + ;
             q.push(*it);
         }
         a.swap(b);
         b.clear();
     }
 }
 int main(){
     int t, i, j, x, y, s, f;
     scanf("%d", &t);
     while(t--){
         scanf("%d %d", &n, &m);
         memset(d, inf, sizeof(d));
         g.clear();
         g.resize(N+);
         for(i = ; i < m; ++i){
             scanf("%d %d", &x, &y);
             g[x].push_back(y);
             g[y].push_back(x);
         }
         scanf("%d", &s);
         d[s] = ;
         bfs(s);
         f = ;
         for(i = ; i <= n; ++i){
             if(i == s)continue;
             if(d[i] == inf)
                 printf("-1\n");
             else if(!f){
                 printf("%d", d[i]);
                 f = ;
             }
             else
                 printf(" %d",d[i]);
         }
         printf("\n");
     }
     return ;
 }