莫队算法？
感觉没什么优越性啊？难道就是因为在排序的时候cmp函数的不同？这样做为什么减少时限啊？
我带着疑惑敲了代码，却一直有bug……
代码：
1 type node=record 2 l,r,id,x,y:int64; 3 end; 4 var a,ans:array[1..55000] of node; 5 s,c,p:array[1..55000] of longint; 6 i,n,m,block,l,r,k:longint; 7 anss:int64; 8 function gcd(x,y:longint):longint; 9 begin 10 if y=0 then exit(x) else exit(gcd(y,x mod y)); 11 end; 12 function cmp(x,y:node):boolean; 13 begin 14 if p[x.l]=p[y.l] then exit(x.r<y.r); 15 exit(x.l<y.l); 16 end; 17 procedure sort(h,l:longint); 18 var i,j:longint; 19 tmp,mm:node; 20 begin 21 i:=h;j:=l;mm:=a[(i+j)>>1]; 22 repeat 23 while cmp(a[i],mm) do inc(i); 24 while cmp(mm,a[j]) do dec(j); 25 if i<=j then 26 begin 27 tmp:=a[i];a[i]:=a[j];a[j]:=tmp; 28 inc(i);dec(j); 29 end; 30 until i>j ; 31 if i<l then sort(i,l); 32 if j>h then sort(h,j); 33 end; 34 procedure init; 35 begin 36 readln(n,m); 37 for i:=1 to n do read(c[i]); 38 block:=trunc(sqrt(n)); 39 for i:=1 to n do p[i]:=(i-1) div block+1; 40 for i:=1 to m do 41 begin 42 readln(a[i].l,a[i].r); 43 a[i].id:=i; 44 end; 45 end; 46 procedure update(p,add:longint); 47 begin 48 dec(anss,sqr(s[c[p]])); 49 inc(s[c[p]],add); 50 inc(anss,sqr(s[c[p]])); 51 end; 52 procedure main; 53 begin 54 sort(1,m); 55 l:=1;r:=0; 56 for i:=1 to m do 57 begin 58 while r<a[i].r do 59 begin 60 update(r+1,1);inc(r); 61 end; 62 while r>a[i].r do 63 begin 64 update(r,-1);dec(r); 65 end; 66 while l<a[i].l do 67 begin 68 update(l,-1);inc(l); 69 end; 70 while l>a[i].l do 71 begin 72 update(l-1,1);dec(l); 73 end; 74 if a[i].l=a[i].r then 75 begin 76 a[i].x:=0;a[i].y:=1; 77 continue; 78 end; 79 with a[i] do 80 begin 81 x:=anss-(r-l+1); 82 y:=(r-l+1)*(r-l); 83 k:=gcd(x,y); 84 x:=x div k;y:=y div k; 85 end; 86 end; 87 for i:=1 to m do ans[a[i].id]:=a[i]; 88 for i:=1 to m do with ans[i] do writeln(x,'/',y); 89 end; 90 begin 91 init; 92 main; 93 end.