每个顶点有且仅有一条出边是什么意思呢
类似一棵树，树上的边都是由儿子指向父亲的，并且这个东西带着一个环
也就是一个个有向环套有向树……
这题还是比较简单的，把环作为根然后类似lca做即可，注意细节的panding
1 type node=record 2 po,next:longint; 3 end; 4 5 var e:array[0..500010] of node; 6 s,p,w,c,be,d,q:array[0..500010] of longint; 7 v:array[0..500010] of boolean; 8 anc:array[0..500010,0..20] of longint; 9 t,f,r,n,m,len,i,x,y,a,b:longint; 10 11 function max(a,b:longint):longint; 12 begin 13 if a>b then exit(a) else exit(b); 14 end; 15 16 function min(a,b:longint):longint; 17 begin 18 if a>b then exit(b) else exit(a); 19 end; 20 21 procedure swap(var a,b:longint); 22 var c:longint; 23 begin 24 c:=a; 25 a:=b; 26 b:=c; 27 end; 28 29 procedure add(x,y:longint); 30 begin 31 inc(len); 32 e[len].po:=y; 33 e[len].next:=p[x]; 34 p[x]:=len; 35 end; 36 37 procedure bfs; 38 var x,i,y:longint; 39 begin 40 f:=1; 41 while f<=r do 42 begin 43 x:=q[f]; 44 for i:=1 to 20 do 45 begin 46 y:=anc[x,i-1]; 47 if y<>0 then anc[x,i]:=anc[y,i-1] else break; 48 end; 49 i:=p[x]; 50 while i<>0 do 51 begin 52 y:=e[i].po; 53 if not v[y] then 54 begin 55 d[y]:=d[x]+1; 56 anc[y,0]:=x; 57 be[y]:=t; 58 inc(r); 59 q[r]:=y; 60 v[y]:=true; 61 end; 62 i:=e[i].next; 63 end; 64 inc(f); 65 end; 66 end; 67 68 procedure lca(x,y:longint); 69 var i,num,a1,b1,a2,b2:longint; 70 begin 71 a:=0; b:=0; 72 if d[x]>d[y] then 73 for i:=20 downto 0 do 74 if d[x]-1 shl i>=d[y] then 75 begin 76 x:=anc[x,i]; 77 a:=a+1 shl i; 78 end; 79 80 if d[y]>d[x] then 81 for i:=20 downto 0 do 82 if d[y]-1 shl i>=d[x] then 83 begin 84 y:=anc[y,i]; 85 b:=b+1 shl i; 86 end; 87 88 if x=y then exit; 89 for i:=20 downto 0 do 90 if (anc[x,i]<>anc[y,i]) then 91 begin 92 x:=anc[x,i]; a:=a+1 shl i; 93 y:=anc[y,i]; b:=b+1 shl i; 94 end; 95 96 if (anc[x,0]=anc[y,0]) and (anc[x,0]<>0) then 97 begin 98 inc(a); inc(b); 99 exit; 100 end; 101 num:=s[be[x]]; 102 if c[x]>c[y] then a1:=a+num-c[x]+c[y] else a1:=a+c[y]-c[x]; 103 b1:=b; 104 a2:=a; 105 if c[x]<c[y] then b2:=b+num-c[y]+c[x] else b2:=b+c[x]-c[y]; 106 if max(a1,b1)=max(a2,b2) then 107 begin 108 if (min(a1,b1)>min(a2,b2)) or (min(a1,b1)=min(a2,b2)) and (a1<b1) then 109 begin 110 a:=a2; 111 b:=b2; 112 end 113 else begin 114 a:=a1; 115 b:=b1; 116 end; 117 end 118 else if max(a1,b1)>max(a2,b2) then 119 begin 120 a:=a2; 121 b:=b2; 122 end 123 else begin 124 a:=a1; 125 b:=b1; 126 end; 127 end; 128 129 begin 130 readln(n,m); 131 for i:=1 to n do 132 begin 133 read(w[i]); 134 add(w[i],i); 135 end; 136 137 for i:=1 to n do 138 if be[i]=0 then 139 begin 140 inc(t); 141 be[i]:=t; 142 x:=i; 143 while true do 144 begin 145 x:=w[x]; 146 if be[x]=t then break; 147 be[x]:=t; 148 end; 149 y:=x; 150 r:=0; 151 repeat 152 inc(s[t]); 153 c[y]:=s[t]; 154 inc(r); 155 q[r]:=y; 156 v[y]:=true; 157 y:=w[y]; 158 until y=x; 159 bfs; 160 end; 161 162 for i:=1 to m do 163 begin 164 readln(x,y); 165 if be[x]<>be[y] then 166 begin 167 writeln('-1 -1'); 168 continue; 169 end; 170 lca(x,y); 171 writeln(a,' ',b); 172 end; 173 end.
