Circle of Friends

강연통 축소점이 점점 손에 잡히는 것 같아요(웃음)
연습할 때 한 번씩 쓸 수 있으면 붙이지 마세요. 정말 좋아요.
강연통 축소점 후 bfs 최단로 구하기
겨우 dfs 세트 bfs?웃다
----------------------나는 코드의 혼절선----------------------

#include<bits/stdc++.h>
using namespace std;

const int maxn = 112345;

vector<int> edge[maxn];
vector<int> dcc[maxn];

int dfn[maxn],low[maxn],_cnt;
int bel[maxn];

stack<int> S;

void init(int n){
    for(int i=0;i<=n;i++){
        edge[i].clear();
        dcc[i].clear();
    }
    memset(dfn,-1,sizeof(dfn));
    memset(low,-1,sizeof(low));
    memset(bel,-1,sizeof(bel));
    _cnt = 0;
    while(S.empty()==false){
        S.pop();
    }
}

#define iter vector<int>::iterator

void dfs(int st){
    dfn[st] = low[st] = _cnt++;
    S.push(st);
    for(iter it = edge[st].begin();it!=edge[st].end();it++){
        int x = *it;
        if(dfn[x] == -1){
            dfs(x);
            low[st] = min(low[st],low[x]);
        }
        else if(bel[x] == -1){
            low[st] = min(low[st],dfn[x]);
        }
    }
    if(low[st] == dfn[st]){
        while(S.top() != st){
            bel[S.top()] = st;
            S.pop();
        }
        bel[st] = st;
        S.pop();
    }
}

int dis[maxn];
queue<int> Q;

int bfs(int st,int ed){
    while(Q.empty()==false)
        Q.pop();
    memset(dis,-1,sizeof(dis));
    dis[st] = st;
    Q.push(st);
    while(Q.empty()==false){
        st = Q.front();
        Q.pop();
        if(st == ed){
            return dis[st];
        }
        for(iter it = dcc[st].begin();it!=dcc[st].end();it++){
            if(dis[*it] == -1){
                dis[*it] = dis[st] +1;
                Q.push(*it);
            }
        }
    }
    return -1;
}

int main(){
    int T;
    scanf("%d",&T);
    int n,m;
    while(T-- && ~scanf("%d %d",&n,&m)){
        init(n);
        int x,y;
        while(m--){
            scanf("%d %d",&x,&y);
            edge[x].push_back(y);
        }
        for(int i=0;i<n;i++){
            if(dfn[i] == -1){
                dfs(i);
            }
        }
        for(int i=0;i<n;i++){
            for(iter it = edge[i].begin();it!=edge[i].end();it++){
                int st = bel[i];
                int ed = bel[*it];
                if(st != ed){
                    dcc[st].push_back(ed);
                }
            }
        }
        printf("%d
",bfs(bel[0],bel[n-1]));
    }
    return 0;
}