Hoj 1520 the bottom of a graph // poj 2553 the bottom of a graph

/*  After the strongly connected component is found to be reduced to a point, the following Tarjan is used to calculate all points with a given degree of 0.AlgorithmThe first is to use the adjacent linked list of the struct, and the second is to use the vector as the adjacent linked list.  */  # Include <Cstdio> # Include <Cstring> Const   Int X = 15002  ;  Int  Dfn [X], low [X], stack [X], Father [X], depth, top, bcnt;  Int  Counter [X], n, m; Bool  Instack [x];  Struct  Node {  Int  V; Node * Next;  Void  Fun () {v = 0  ; Next = Null ;}} edge [X], * Head [X], * TMP;  Void Tarjan ( Int U ){  Int  V; dfn [u] = Low [u] = ++ Depth; stack [ ++ Top] = U; instack [u] = True  ;  For (Node * P = head [u]; P = p-> Next) {v = P-> V;  If (! Low [v]) {Tarjan (v );  If (Low [v] <Low [u]) low [u] = Low [v];}  Else   If (Instack [v] & low [u]> Dfn [v]) low [u] = Dfn [v];}  If (Low [u] = Dfn [u]) {bcnt ++ ;  Do  {V = Stack [top -- ]; Instack [v] =False  ; Father [v] = Bcnt ;}  While (U! = V );}}  Void  Solve () {top = Depth = bcnt = 0  ; Memset (instack,  False , Sizeof  (Instack); memset (low,  0 , Sizeof (Low); memset (counter,  0 , Sizeof  (Counter ));  For ( Int I = 1 ; I <= N; I ++ )  If (! Low [I]) Tarjan (I );  For ( Int I = 1 ; I <= N; I ++ ) For (Node * P = head [I]; P = p-> Next)  If (Father [I]! = Father [p-> V]) Counter [Father [I] ++ ;  Bool Flag = False  ;  For ( Int I = 1 ; I <= N; I ++ )  If (!Counter [Father [I]) {  If  (FLAG) printf (  "   "  );  Else  Flag = True  ; Printf (  "  % D  "  , I);} printf (  " \ N  "  );}  Int  Main () {freopen (  "  Sum. In  " , "  R  "  , Stdin); freopen (  "  Sum. Out  " , "  W "  , Stdout );  Int  U, V;  While (Scanf ( "  % D  " ,& N), n) {scanf (  "  % D  " ,& M); memset (Head, null,  Sizeof  (Head ));  For ( Int I = 0 ; I <m; I ++ ) Edge [I]. Fun (); TMP = Edge;  For ( Int I = 0 ; I <m; I ++ ) {Scanf (  "  % D  " , & U ,& V); TMP -> Next = Head [u]; TMP -> V = V; head [u] = TMP ++ ;} Solve ();}  Return   0  ;}  /*  Vector as an adjacent linked list  */  # Include <Vector> # Include <Cstdio> # Include <Cstring> Using   Namespace  STD; Const   Int X = 15005  ;  Int  Dfn [X], low [X], Father [X], stack [X], bcnt, top, depth;  Int  Counter [X], n, m;  Bool  Instack [X]; vector < Int > Adj [x];  Void Tarjan ( Int  U) {LOW [u] = Dfn [u] = ++ Depth; instack [u] = True  ; Stack [ ++ Top] = U;  Int V, Len = Adj [u]. Size ();  For ( Int I = 0 ; I <Len; I ++ ) {V = Adj [u] [I];  If (!Low [v]) {Tarjan (V); low [u] = Min (low [u], low [v]);}  Else   If  (Instack [v]) low [u] = Min (low [u], dfn [v]);}  If (Low [u] = Dfn [u]) { ++ Bcnt;  Do  {V = Stack [top -- ]; Instack [v] =False  ; Father [v] = Bcnt ;}  While (U! = V );}}  Void  Solve () {depth = Top = bcnt = 0  ; Memset (low,  0 , Sizeof  (Low); memset (instack,  False , Sizeof (Instack); memset (counter,  0 , Sizeof  (Counter ));  For ( Int I = 1 ; I <= N; I ++ )  If (! Low [I]) Tarjan (I );  Int  Len;  For ( Int I =1 ; I <= N; I ++ ) {Len = Adj [I]. Size ();  For ( Int J = 0 ; J <Len; j ++ )  If (Father [I]! = Father [adj [I] [J]) Counter [Father [I] ++ ;}  Bool Flag = False  ; For ( Int I = 1 ; I <= N; I ++ )  If (! Counter [Father [I]) {  If  (FLAG) printf (  "   "  );  Else  Flag = True ; Printf (  "  % D  "  , I);} printf (  "  \ N  "  );}  Int  Main () {freopen (  "  Sum. In  " , "  R  " , Stdin); freopen (  "  Sum. Out  " , "  W  "  , Stdout );  Int  U, V;  While (Scanf ( "  % D  " ,& N), n) {scanf (  " % D  " ,& M );  For ( Int I = 1 ; I <= N; I ++ ) Adj [I]. Clear ();  For ( Int I = 0 ; I <m; I ++ ) {Scanf (  "  % D  " , & U ,&V); adj [u]. push_back (V);} solve ();}  Return   0  ;}