1 #include <iostream> 2 #include <cstdlib> 3 #include <cstdio> 4 const int inf = 1 << 30 , maxn = 45 ; 5 using namespace std ; 6 int n , jv[maxn][maxn] ; 7 inline void Init( ) 8 { 9     freopen( "magic.in" , "r" , stdin ) ;10     freopen( "magic.out" , "w" , stdout ) ;11 }12 13 int read( )14 {15     char ch = getchar( ) ; int k = 1 , ret = 0 ;16     while( ch < ‘0‘ || ch > ‘9‘ ) { if( ch == ‘-‘ )k = -1 ; ch = getchar( ) ; }17     while( ch >= ‘0‘ && ch <= ‘9‘ ) ret = ret * 10 + ch - ‘0‘ , ch = getchar( ) ;18     return ret * k ;19 }20 21 22 void sov(  )23 {24     int x = 1 , y = (1+n)>>1 ;25     jv[x][y] = 1 ; 26     for( int i = 2 ; i <= n*n ; ++i )27     {28         if( x == 1 && y != n )29         {30             jv[n][y+1] = i ;31             x = n ; ++y ;32             continue ;33         }34         if( y == n && x != 1 )35         {36             jv[x-1][1] = i ;37             --x ; y = 1 ;38             continue ;39         }40         if( x == 1 && y == n )41         {42             jv[x+1][y] = i ;43             ++x ; continue ;44         }45         else46         {47             if( !jv[x-1][y+1] ) 48             {49                 jv[x-1][y+1] = i ;50                 --x ; ++y ;51                 continue ;52             }53             jv[x+1][y] = i ;54             ++x ; continue ;55         }56     }57 }58 59 void output( )60 {61     for( int x = 1 ; x <= n ; ++x )62     {63         for( int y = 1 ; y <= n ; ++y )    64             printf( "%d " , jv[x][y] ) ;65         printf( "\n" ) ;66     }67 }68 69 70 int main( )71 {    72     Init( ) ; 73     n = read( ) ;74     sov( ) ;75     output( ) ;76     fclose( stdin ) ;77     fclose( stdout ) ;78     return 0 ;79 }

 1 #include <iostream> 2 #include <cstdlib> 3 #include <cstdio> 4 const int inf = 1 << 30 , maxn =  200000 + 11  ; 5 using namespace std ; 6 int n , fa[maxn][2] ; //father and dis 7  8 inline void Init( ) 9 {10     freopen( "message.in" , "r" , stdin ) ;11     freopen( "message.out" , "w" , stdout ) ;12 }13 14 int read( )15 {16     char ch = getchar( ) ; int k = 1 , ret = 0 ;17     while( ch < ‘0‘ || ch > ‘9‘ ) { if( ch == ‘-‘ )k = -1 ; ch = getchar( ) ; }18     while( ch >= ‘0‘ && ch <= ‘9‘ ) ret = ret * 10 + ch - ‘0‘ , ch = getchar( ) ;19     return ret * k ;20 }21 22 int find( int x )23 {24     if( fa[x][0] == x ) return x ;25     int fu = fa[x][0] ;26     fa[x][0] = find( fa[x][0] ) ;27     fa[x][1] += fa[fu][1] ;28     return fa[x][0] ;29 }30 31 32 void sov( ) 33 {34     for( int x = 1 ; x <= n ; ++x ) fa[x][0] = x ;35     int y , root1 , root2 , ans = inf ; 36     for( int x = 1 ; x <= n ; ++x )37     {38         y = read( ) ;39         root1 = find( x ) , root2 = find( y ) ;40         if( root1 != root2 )41         {42             fa[root1][0] = root2 ;43             fa[root1][1] += 1 + fa[y][1] ;44         }45         else 46             ans = min( ans , fa[x][1] + fa[y][1] + 1 ) ;47     }48     printf( "%d\n" , ans ) ;49 }50 51 52 int main( )53 {    54     Init( ) ; 55     n = read( ) ;56     sov( ) ;57     fclose( stdin ) ;58     fclose( stdout ) ;59     return 0 ;60 }

 1 #include <iostream> 2 #include <cstdlib> 3 #include <cstdio> 4 #include <queue> 5 const int inf = 1 << 30 , maxn =  200000 + 11  ; 6 using namespace std ; 7 queue < int > Q ; 8 struct id 9 {10     int nxt , in ; bool vis ;11 } node[maxn] ;12 int n , ans = 0 ;13 14 inline void Init( )15 {16     freopen( "message.in" , "r" , stdin ) ;17     freopen( "message.out" , "w" , stdout ) ;18 }19 20 int read( )21 {22     char ch = getchar( ) ; int k = 1 , ret = 0 ;23     while( ch < ‘0‘ || ch > ‘9‘ ) { if( ch == ‘-‘ )k = -1 ; ch = getchar( ) ; }24     while( ch >= ‘0‘ && ch <= ‘9‘ ) ret = ret * 10 + ch - ‘0‘ , ch = getchar( ) ;25     return ret * k ;26 }27 28 void input(  )29 {30     n  = read( ) ;31     for( int x = 1 ; x <= n ; ++x )32         node[x].nxt = read( ) , node[node[x].nxt].in++ ;    33 }34 35 36 void sov( )37 {38     for( int x = 1 ; x <= n ; ++x ) if( !node[x].in ) { Q.push( x ) ; node[x].vis = true ; }39     while( !Q.empty( ) )40     {41         int u = Q.front( ) ; Q.pop( ) ;    42         int v = node[u].nxt ;43         if( --node[v].in == 0 ) { Q.push( v ) ; node[v].vis = true ; }44     } ans = inf ; 45     for( int x = 1 ; x <= n ; ++x )46     {47         int cnt = 1 , j = node[x].nxt ; 48         if( !node[x].vis )49         {50             while( j != x )51             {52                 cnt++ ;53                 node[j].vis = true ;54                 j = node[j].nxt ;55             }56             ans = min( ans , cnt ) ;57         }58         59     }60     printf( "%d\n" , ans ) ;61 }62 63 64 int main( )65 {    66     Init( ) ; 67     input(  ) ;68     sov( ) ;69     fclose( stdin ) ;70     fclose( stdout ) ;71     return 0 ;72 }