會構建虛樹之后就是noip提高組的題目了
稍微難一點的是求代價和，只要注意按一個方向避免重復計算貢獻即可

1 const inf=100000000; 2 type node=record 3 po,next:longint; 4 end; 5 6 var mi,mx,fa,p,q,size,d,a,b:array[0..1000010] of longint; 7 e:array[0..2000010] of node; 8 f:array[0..1000010] of int64; 9 v:array[0..1000010] of boolean; 10 anc:array[0..1000010,0..21] of longint; 11 ans2,ans3,z,t,h,i,len,n,m,s,j,x,y:longint; 12 dis,ans1:int64; 13 14 procedure add(x,y:longint); 15 begin 16 inc(len); 17 e[len].po:=y; 18 e[len].next:=p[x]; 19 p[x]:=len; 20 end; 21 22 procedure swap(var a,b:longint); 23 var c:longint; 24 begin 25 c:=a; 26 a:=b; 27 b:=c; 28 end; 29 30 function max(a,b:longint):longint; 31 begin 32 if a>b then exit(a) else exit(b); 33 end; 34 35 function min(a,b:longint):longint; 36 begin 37 if a>b then exit(b) else exit(a); 38 end; 39 40 procedure dfs(x:longint); 41 var i,y:longint; 42 begin 43 inc(h); 44 a[x]:=h; 45 i:=p[x]; 46 while i<>0 do 47 begin 48 y:=e[i].po; 49 if fa[x]<>y then 50 begin 51 fa[y]:=x; 52 anc[y,0]:=x; 53 d[y]:=d[x]+1; 54 dfs(y); 55 end; 56 i:=e[i].next; 57 end; 58 end; 59 60 procedure sort(l,r:longint); 61 var i,j,x:longint; 62 begin 63 i:=l; 64 j:=r; 65 x:=a[b[(l+r) shr 1]]; 66 repeat 67 while a[b[i]]<x do inc(i); 68 while x<a[b[j]] do dec(j); 69 if not(i>j) then 70 begin 71 swap(b[i],b[j]); 72 inc(i); 73 dec(j); 74 end; 75 until i>j; 76 if l<j then sort(l,j); 77 if i<r then sort(i,r); 78 end; 79 80 function lca(x,y:longint):longint; 81 var i,p:longint; 82 begin 83 if x=y then exit(x); 84 if d[x]<d[y] then swap(x,y); 85 p:=trunc(ln(d[x])/ln(2)); 86 if d[x]>d[y] then 87 for i:=p downto 0 do 88 if d[x]-1 shl i>=d[y] then x:=anc[x,i]; 89 if x=y then exit(x); 90 for i:=p downto 0 do 91 if (anc[y,i]<>anc[x,i]) then 92 begin 93 x:=anc[x,i]; 94 y:=anc[y,i]; 95 end; 96 exit(fa[x]); 97 end; 98 99 procedure dp(x:longint); 100 var i,y:longint; 101 begin 102 f[x]:=0; 103 if v[x] then 104 begin 105 size[x]:=1; //size[]表示虛樹中包含的關鍵點個數 106 mi[x]:=0; 107 mx[x]:=0; 108 end 109 else begin 110 size[x]:=0; 111 mi[x]:=inf; 112 mx[x]:=-inf; 113 end; 114 i:=p[x]; 115 while i<>0 do 116 begin 117 y:=e[i].po; 118 dp(y); 119 dis:=d[y]-d[x]; 120 ans1:=ans1+(f[x]+int64(size[x])*dis)*int64(size[y])+f[y]*int64(size[x]); 121 size[x]:=size[x]+size[y]; 122 f[x]:=f[x]+f[y]+int64(size[y])*dis; 123 ans2:=min(ans2,mi[x]+dis+mi[y]); 124 ans3:=max(ans3,mx[x]+dis+mx[y]); 125 mx[x]:=max(mx[x],dis+mx[y]); 126 mi[x]:=min(mi[x],dis+mi[y]); 127 i:=e[i].next; 128 end; 129 p[x]:=0; 130 end; 131 132 begin 133 readln(n); 134 for i:=1 to n-1 do 135 begin 136 readln(x,y); 137 add(x,y); 138 add(y,x); 139 end; 140 dfs(1); 141 t:=trunc(ln(n)/ln(2)); 142 for i:=1 to t do 143 for j:=1 to n do 144 begin 145 y:=anc[j,i-1]; 146 if y<>0 then anc[j,i]:=anc[y,i-1]; 147 end; 148 fillchar(p,sizeof(p),0); 149 readln(m); 150 for i:=1 to m do 151 begin 152 readln(s); 153 for j:=1 to s do 154 begin 155 read(b[j]); 156 v[b[j]]:=true; 157 end; 158 readln; 159 sort(1,s); 160 ans1:=0; 161 ans2:=inf; 162 ans3:=0; 163 len:=0; 164 t:=1; 165 q[1]:=1; 166 for j:=1 to s do 167 begin 168 x:=b[j]; 169 z:=lca(x,q[t]); 170 while d[z]<d[q[t]] do 171 begin 172 if d[z]>=d[q[t-1]] then 173 begin 174 add(z,q[t]); 175 dec(t); 176 if q[t]<>z then 177 begin 178 inc(t); 179 q[t]:=z; 180 end; 181 break; 182 end; 183 add(q[t-1],q[t]); 184 dec(t); 185 end; 186 if q[t]<>x then 187 begin 188 inc(t); 189 q[t]:=x; 190 end; 191 end; 192 while t>1 do 193 begin 194 add(q[t-1],q[t]); 195 dec(t); 196 end; 197 dp(1); 198 writeln(ans1,' ',ans2,' ',ans3); 199 for j:=1 to s do 200 v[b[j]]:=false; 201 end; 202 end. View Code

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轉載于:https://www.cnblogs.com/phile/p/4472965.html

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