POJ 3368 RMQ

#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <cstdio>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#define eps 1e-5
#define MAXN 111111
#define MAXM 11111
#define INF 1000000000
using namespace std;
int mx[MAXN][18], Log[MAXN];
struct PP
{
int left, right, num;
} p[MAXN];
int v[MAXN], h[MAXN];
int n, m, len;
void rmqinit()
{
for(int i = 1; i <= n; i++) mx[i][0] = p[i].num;
int m = Log
;
for(int i = 1; i <= m; i++)
for(int j = 1; j <= n; j++)
{
mx[j][i] = mx[j][i - 1];
if(j + (1 << (i - 1)) <= n) mx[j][i] = max(mx[j][i], mx[j + (1 << (i - 1))][i - 1]);
}
}
int rmqmax(int l, int r)
{
int m = Log[r - l + 1];
return max(mx[l][m] , mx[r - (1 << m) + 1][m]);
}
void get()
{
len = 1;
p[1].left = 1;
p[1].num = 1;
h[1] = 1;
for(int i = 2; i <= n; i++)
{
if(v[i] == v[i - 1])
p[len].num++;
else
{
p[len++].right = i - 1;
p[len].left = i;
p[len].num = 1;
}
h[i] = len;
}
p[len].right = n;
}
int in()
{
int flag = 1;
char ch;
int a = 0;
while((ch = getchar()) == ' ' || ch == '\n');
if(ch == '-') flag = -1;
else
a += ch - '0';
while((ch = getchar()) != ' ' && ch != '\n')
{
a *= 10;
a += ch - '0';
}
return flag * a;
}
void out(int a)
{
if(a < 0)
{
putchar('-');
a = -a;
}
if(a >= 10)out(a / 10);
putchar(a % 10 + '0');
}
int main()
{
Log[1] = 0;
for(int i = 2; i < MAXN; i++) Log[i] = Log[i >> 1] + 1;
while(scanf("%d", &n) != EOF && n)
{
scanf("%d", &m);
for(int i = 1; i <= n; i++) v[i] = in();
get();
n = len;
rmqinit();
for(int i = 1; i <= m; i++)
{
int x, y;
x= in();
y = in();
int u = h[x];
int v = h[y];
if(u == v) out(y - x + 1);
else if(u == v - 1) out(max(p[u].right - x + 1, y - p[v].left + 1));
else
{
int ans = max(p[u].right - x + 1, y - p[v].left + 1);
int t = rmqmax(u + 1, v - 1);
ans = max(ans, t);
out(ans);
}
putchar('\n');
}
}
return 0;
}