【BZOJ3238】差异（后缀数组，单调栈）

  1 var x,y,sa,rank,height,wc,wd,a:array[0..600000]of longint;
  2     l,r:array[1..600000]of int64;
  3     stk:array[1..600000]of longint;
  4     n,i,m,top:longint;
  5     ans,j:int64;
  6     ch:ansistring;
  7 
  8 function min(x,y:longint):longint;
  9 begin
 10  if x<y then exit(x);
 11  exit(y);
 12 end;
 13 
 14 function cmp(a,b,l:longint):boolean;
 15 begin
 16  exit((y[a]=y[b])and(y[a+l]=y[b+l]));
 17 end;
 18 
 19 procedure swap(var x,y:longint);
 20 var t:longint;
 21 begin
 22  t:=x; x:=y; y:=t;
 23 end;
 24 
 25 procedure getsa(n:longint);
 26 var i,j,p:longint;
 27 begin
 28  for i:=0 to n-1 do
 29  begin
 30   x[i]:=a[i];
 31   inc(wc[x[i]]);
 32  end;
 33  for i:=1 to m-1 do wc[i]:=wc[i-1]+wc[i];
 34  for i:=n-1 downto 0 do
 35  begin
 36   dec(wc[x[i]]);
 37   sa[wc[x[i]]]:=i;
 38  end;
 39  j:=1; p:=1;
 40  while p<n do
 41  begin
 42   p:=0;
 43   for i:=n-j to n-1 do
 44   begin
 45    y[p]:=i; inc(p);
 46   end;
 47   for i:=0 to n-1 do
 48    if sa[i]>=j then begin y[p]:=sa[i]-j; inc(p); end;
 49   for i:=0 to n-1 do wd[i]:=x[y[i]];
 50   for i:=0 to m-1 do wc[i]:=0;
 51   for i:=0 to n-1 do inc(wc[wd[i]]);
 52   for i:=1 to m-1 do wc[i]:=wc[i-1]+wc[i];
 53   for i:=n-1 downto 0 do
 54   begin
 55    dec(wc[wd[i]]);
 56    sa[wc[wd[i]]]:=y[i];
 57   end;
 58   for i:=0 to n do swap(x[i],y[i]);
 59   p:=1; x[sa[0]]:=0;
 60   for i:=1 to n-1 do
 61    if cmp(sa[i-1],sa[i],j) then x[sa[i]]:=p-1
 62     else begin x[sa[i]]:=p; inc(p); end;
 63   j:=j<<1;
 64   m:=p;
 65  end;
 66 end;
 67 
 68 procedure getheight(n:longint);
 69 var i,j,k:longint;
 70 begin
 71  k:=0;
 72  for i:=1 to n do rank[sa[i]]:=i;
 73  for i:=0 to n-1 do
 74  begin
 75   if k>0 then dec(k);
 76   j:=sa[rank[i]-1];
 77   while a[i+k]=a[j+k] do inc(k);
 78   height[rank[i]]:=k;
 79  end;
 80 end;
 81 
 82 begin
 83  assign(input,‘bzoj3238.in‘); reset(input);
 84  assign(output,‘bzoj3238.out‘); rewrite(output);
 85  readln(ch);
 86  n:=length(ch);
 87  for i:=0 to n-1 do a[i]:=ord(ch[i+1])-ord(‘a‘)+1;
 88  a[n]:=0; m:=300;
 89  getsa(n+1);
 90  getheight(n);
 91  stk[1]:=1; height[1]:=-maxlongint; top:=1;
 92  for i:=2 to n do
 93  begin
 94   while (top>0)and(height[i]<height[stk[top]]) do dec(top);
 95   if stk[top]=1 then l[i]:=2
 96    else l[i]:=stk[top]+1;
 97   inc(top); stk[top]:=i;
 98  end;
 99 
100  stk[1]:=n+1; height[n+1]:=-maxlongint; top:=1;
101  for i:=n downto 2 do
102  begin
103   while (top>0)and(height[i]<=height[stk[top]]) do dec(top);
104   if stk[top]=n+1 then r[i]:=n
105    else r[i]:=stk[top]-1;
106   inc(top); stk[top]:=i;
107  end;
108 
109 
110  ans:=int64(n-1)*int64(n)*(n+1) div 2;
111  for i:=2 to n do ans:=ans-2*(-l[i]+i+1)*(r[i]-i+1)*height[i];
112  //for i:=2 to n+1 do writeln(l[i],‘ ‘,r[i]);
113  writeln(ans);
114  close(input);
115  close(output);
116 end.