poj3368--线段树统计区间的最大频率

import java.io.*;

public class Main {
static StreamTokenizer in = new StreamTokenizer(new BufferedReader(
new InputStreamReader(System.in)));
static  PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
final static  int nextInt() throws IOException {
in.nextToken();
return (int) in.nval;
}

class Node
{
int left,right;
int lenum,rignum;//信息域，存储该区间的左右端的元素是什么
int num,lnum,rnum;//存储左端的长度和右端长度以及最长的

Node(int left,int right)
{
this.left=left;
this.right=right;
}

int mid()
{
return (right+left)>>1;
}
int lenght()
{
return (right-left+1);
}
}
static int number;
static int MAX=100010;
static Node tree[]=new Node[MAX<<2];
static int data[]=new int[MAX];

void build(int left,int right,int idx) throws IOException
{
//		 System.out.println(idx+"&^&^&");
tree[idx]=new Node(left,right);
tree[idx].left=left;
tree[idx].right=right;
if(tree[idx].left==tree[idx].right)
{
tree[idx].lenum=tree[idx].rignum=data[left];
//			System.out.println(data[left]);
tree[idx].lnum=tree[idx].rnum=tree[idx].num=1;
return;
}

int mid=tree[idx].mid();
build(left,mid,idx<<1);
build(mid+1,right,idx<<1|1);

tree[idx].num=tree[idx<<1].num;
if(tree[idx<<1|1].num>tree[idx].num)
tree[idx].num=tree[idx<<1|1].num;

if(tree[idx<<1].rnum+tree[idx<<1|1].lnum>tree[idx].num&&tree[idx<<1].rignum==tree[idx<<1|1].lenum)
{
tree[idx].num=tree[idx<<1].rnum+tree[idx<<1|1].lnum;
}

tree[idx].lenum=tree[idx<<1].lenum;
tree[idx].rignum=tree[idx<<1|1].rignum;
tree[idx].lnum=tree[idx<<1].lnum;
tree[idx].rnum=tree[idx<<1|1].rnum;

if(tree[idx<<1].lnum==tree[idx<<1].lenght()&&tree[idx<<1].rignum==tree[idx<<1|1].lenum)
tree[idx].lnum=tree[idx<<1].lnum+tree[idx<<1|1].lnum;
if(tree[idx<<1|1].rnum==tree[idx<<1|1].lenght()&&tree[idx<<1|1].lenum==tree[idx<<1].rignum)
tree[idx].rnum=tree[idx<<1|1].rnum+tree[idx<<1].rnum;
}

int query(int a,int b,int idx)
{
//		System.out.println("idx"+idx);
if(tree[idx].left==a&&tree[idx].right==b)
{

return tree[idx].num;
}

int mid=tree[idx].mid();
//		System.out.println("MID"+mid);
int ans1=-1,ans2=-1,ans3=-1,ans=-1;
if(mid>=b)
{
return query(a,b,idx<<1);
}else if(mid<a)
{
return query(a,b,idx<<1|1);
}
else
{
int temp1=query(a,mid,idx<<1);
int temp2=query(mid+1,b,idx<<1|1);
ans3=Math.max(temp1,temp2);
int temp=-1;
if(tree[idx<<1].rignum==tree[idx<<1|1].lenum)
{
if(mid-tree[idx<<1].rnum+1>=a)
{
a=mid-tree[idx<<1].rnum+1;
}
if(mid+tree[idx<<1|1].lnum<=b)
b=mid+tree[idx<<1|1].lnum;

temp=b-a+1;
}
ans3=Math.max(ans3, temp);
return ans3;
}
}

void run() throws IOException
{

while((number=nextInt())!=0)
{
int qnum=nextInt();
for(int i=1;i<=number;i++)
data[i]=nextInt();
build(1,number,1);
for(int i=1;i<=qnum;i++)
{
int a=nextInt();
int b=nextInt();
int ans=query(a,b,1);
System.out.println(ans);
}

}

}

public static void main(String[] args) throws IOException {

new Main().run();

}

}