題意：

思路：

C++

 1 #include<map>
 2 #include<set>
 3 #include<cmath>
 4 #include<cstdio>
 5 #include<vector>
 6 #include<cstring>
 7 #include<cstdlib>
 8 #include<iostream>
 9 #include<algorithm>
10 #define M 1000000
11 #define MAXN 210000
12 using namespace
 
 std;
13 
14 int g[MAXN][20];
15 int last[M*3];
16 int a[MAXN],st[MAXN],f[MAXN];
17 
18 int ask(int x,int y)
19 {
20   if(x>y) return 0; 
21   int len=y-x+1; int l=log(len)/log(2);
22   return max(g[x][l],g[y-(1<<l)+1][l]);    
23 }
24 
25 int main()
26 {
27     freopen("data.in","r",stdin);
28
 
     freopen("1.out","w",stdout);
29     int n,m,x,y;
30     scanf("%d%d",&n,&m);
31     for(int i=1;i<=n;i++)
32     {
33         scanf("%d",&a[i]);
34         a[i]+=M;
35         st[i]=max(st[i-1],last[a[i]]+1);
36         last[a[i]]=i;
37         g[i][0]=f[i]=i-st[i]+1;
38     } 
39     int
 
 l=log(n)/log(2);
40     for(int i=1;i<=l;i++)
41      for(int j=1;j+(1<<(i-1))<=n;j++) 
42       g[j][i]=max(g[j][i-1],g[j+(1<<(i-1))][i-1]); 
43     for(int i=1;i<=m;i++)
44     {
45         scanf("%d%d",&x,&y);
46         x++; y++; 
47         int l=x; int r=y; 
48         int tmp=x;
49         while(l<=r)
50         {
51             int mid=(l+r)/2;
52             if(st[mid]<x) {tmp=mid;l=mid+1;}
53              else r=mid-1;
54         } 
55         int ans=max(tmp-x+1,ask(tmp+1,y));
56         printf("%d\n",ans);
57     } 
58     return 0;
59 }
60  

pascal

 1 const maxn=200000;
 2       max=1000000;
 3 var n,m,i,x,y,t,j,ans,keypoint,l,r:longint;
 4     a,opt,pre:array[1..maxn]of longint;
 5     rmq:array[1..maxn,0..20]of longint;
 6     f:array[-max..max]of longint;
 7     ch:char;
 8 function find(x,y:longint):longint;
 9   var left,right,mid:longint;
10   begin
11     left:=x;right:=y;
12     while left<=right do begin
13       mid:=(left+right)shr 1;
14       if pre[mid]<=y then left:=mid+1
15       else right:=mid-1;
16     end;
17     find:=left;
18   end;
19 function findmax(x,y:longint):longint;
20   var i,j:longint;
21   begin
22     i:=0;j:=1;
23     while 2*j<=y-x+1 do begin
24       inc(i);
25       j:=j*2;
26     end;
27     if rmq[x,i]>rmq[y+1-j,i] then findmax:=rmq[x,i]
28     else findmax:=rmq[y+1-j,i];
29   end;
30 begin
31   assign(input,‘data.in‘); reset(input);
32   assign(output,‘right.out‘); rewrite(output);
33   readln(n,m);
34   for i:=1 to n do read(a[i]);
35   fillchar(f,sizeof(f),0);
36   opt[n]:=1;
37   pre[n]:=n;
38   f[a[n]]:=n;
39   for i:=n-1 downto 1 do begin
40     opt[i]:=opt[i+1]+1;
41     pre[i]:=pre[i+1];
42     if (f[a[i]]>0)and(f[a[i]]-i<opt[i]) then begin
43        opt[i]:=f[a[i]]-i;
44        pre[i]:=f[a[i]]-1;
45     end;
46     f[a[i]]:=i;
47   end;
48   fillchar(rmq,sizeof(rmq),0);
49   for i:=1 to  n do rmq[i,0]:=opt[i];
50   i:=1;t:=2;
51   while t<=n do begin
52     for j:=1 to n-t+1 do begin
53       if rmq[j,i-1]>rmq[j+(1 shl (i-1)),i-1] then rmq[j,i]:=rmq[j,i-1]
54       else rmq[j,i]:=rmq[j+(1 shl (i-1)),i-1]
55     end;
56     inc(i);
57     t:=t*2;
58   end;
59   for i:=1 to m do begin
60     readln(l,r);
61     inc(l);inc(r);
62     if l>r then begin
63        j:=l;l:=r;r:=j;
64     end;
65     keypoint:=find(l,r);
66     ans:=0;
67     if keypoint>l then ans:=findmax(l,keypoint-1);
68     if (keypoint<=r)and(r-keypoint+1>ans) then begin
69        ans:=r-keypoint+1;
70     end;
71     writeln(ans);
72   end;
73   close(input);
74   close(output);
75 end.

【LibreOJ？？】與眾不同（RMQ，二分）