2009国家集训队小Z的袜子

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.              

2009国家集训队小Z的袜子