Luo Gu P3388 [template] cut point (Tarjan)

Title Description

Given a n- n-point, m -free edges to FIG. M, seeking cut points of FIG.

Input Format

The first line of input n-, m n- , m

The following m m lines each input X, Y X , Y denotes X X to Y Y there is an edge

Output Format

The first output line number cutpoint

The second line node according to an output node from small to large numbers, separated by space

Sample input and output

Entry

6 7
1 2
1 3
1 4
2 5
3 5
4 5
5 6

Export 

1 
5

Description / Tips

For all data, n- ≤ 2 0 0 0 0, m ≤ . 1 0 0 0 0 0

The numbered points are> 0, <= n-

tarjan drawings are not necessarily Unicom

 

. 1 #include <bits / STDC ++ H.>
 2  the using  namespace STD;
 . 3  
. 4  const  int N = 1E5 + . 5 ;
 . 5  int n-, m, DEP;
 . 6  int DFN [N], Low [N];
 . 7 Vector < int > G [N]; /// adjacent table stored FIG 
. 8  SET < int > ST; /// memory cutpoint 
. 9  
10  void Tarjan ( int U, int Father) {
 . 11      DFN [U] = Low [U] = ++ DEP ;
 12 is      int Child = 0 ;
13 is      for ( int I = 0 ; I <G [U] .size (); I ++ ) {
 14          int V = G [U] [I];
 15          IF (! DFN [V]) { /// point not visited 
16              Tarjan (V, Father);
 . 17              Low [U] = min (Low [U], Low [V]);
 18 is              IF (U == Father) { /// root subtree quantity statistics 
. 19                  child ++ ;
 20 is              }
 21 is              the else {
 22 is                  IF (DFN [U] <= Low [V])
 23 is                      st.insert (U);
 24              }
25          }
 26 is          the else Low [U] = min (Low [U], DFN [V]);
 27      }
 28      IF (U == && Child Father> = 2 ) /// as a root node and a number of sub-tree is greater than 1, is cut point 
29          st.insert (U);
 30  }
 31 is  
32  int main () {
 33 is      Scanf ( " % D% D " , & n-, & m);
 34 is      the while (M-- ) {
 35          int X, Y;
 36          Scanf ( " % D% D " , & X, & Y);
 37 [          G [X] .push_back (Y);/// undirected graph, deposit bidirectional edge 
38 is          G [Y] .push_back (X);
 39      }
 40      for ( int I = 0 ; I <n-; I ++ ) {
 41 is          DEP = 0 ; // drawings are not necessarily communication, each set to 0 
42 is          IF (! {DFN [I])
 43 is              Tarjan (I, I);
 44 is          }
 45      }
 46 is      the printf ( " % D \ n- " , st.size ());
 47      int In Flag = 0 ;
 48      for ( SET < int>::iterator it=st.begin();it!=st.end();it++){
49         if(flag) printf(" ");
50         else flag=1;
51         printf("%d",*it);
52     }
53     printf("\n");
54 }