poj 2452

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<iostream>
 5 #include<cmath>
 6 #include<queue>
 7 #define inc(i,l,r) for(i=l;i<=r;i++)
 8 #define dec(i,l,r) for(i=l;i>=r;i--)
 9 #define inf 1e9
10 #define mem(a) memset(a,0,sizeof(a))
11 #define ll long long
12 #define succ(x) (1<<x)
13 #define NM 50000+5
14 using namespace std;
15 int read(){
16     int x=0,f=1;char ch=getchar();
17     while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();}
18     while(isdigit(ch))x=x*10+ch-‘0‘,ch=getchar();
19     return x*f;
20 }
21 int ans,n,i,a[NM],f[NM][25],d[NM][25],j,p;
22 int _max(int x,int y){
23     return a[x]<a[y]?y:x;
24 }
25 int _min(int x,int y){
26     return a[x]<a[y]?x:y;
27 }
28 int maxn(int l,int r){
29     int k=log(r-l+1.0)/log(2.0);
30     return _max(d[l][k],d[r-succ(k)+1][k]);
31 }
32 int minn(int l,int r){
33     int k=log(r-l+1.0)/log(2.0);
34     return _min(f[l][k],f[r-succ(k)+1][k]);
35 }
36 int erfen(int x,int l,int r){
37     while(l<r){
38         int t=l+r>>1;
39         if(x<a[minn(l,t)])
40         l=t+1;else r=t;
41     }
42     return r;
43 }
44 int main(){
45     while(~scanf("%d",&n)){
46         ans=0;
47         inc(i,1,n)f[i][0]=d[i][0]=i,a[i]=read();
48         p=log(n+1.0)/log(2.0);
49         inc(j,1,p)
50         for(i=1;i+succ(j-1)-1<=n;i++)
51         d[i][j]=_max(d[i][j-1],d[i+succ(j-1)][j-1]),
52         f[i][j]=_min(f[i][j-1],f[i+succ(j-1)][j-1]);
53         inc(i,1,n){
54             j=erfen(a[i],i+1,n);
55             j=maxn(i,j);
56             ans=max(ans,j-i);
57         }
58         if(ans==0)ans=-1;
59         printf("%d\n",ans);
60     }
61     return 0;
62 }