BZOJ1636: [Usaco2007 Jan]Balanced Lineup

 1 #include<cstdio>
 2 #include<cmath>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<iostream>
 6 #define maxn 50000+100
 7 #define maxm 100000
 8 using namespace std;
 9 int n,m,a[maxn],f[maxn][16],g[maxn][16];
10 inline int read()
11 {
12     int x=0,f=1;char ch=getchar();
13     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
14     while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
15     return x*f;
16 }
17 void rmq()
18 {
19     for(int i=1;i<=n;i++)f[i][0]=a[i];
20     for(int i=1;i<=floor(log(n)/log(2));i++)
21      for(int j=1;j<=n-(1<<i)+1;j++)
22       f[j][i]=max(f[j][i-1],f[j+(1<<(i-1))][i-1]);
23     for(int i=1;i<=n;i++)g[i][0]=a[i];
24     for(int i=1;i<=floor(log(n)/log(2));i++)
25      for(int j=1;j<=n-(1<<i)+1;j++)
26       g[j][i]=min(g[j][i-1],g[j+(1<<(i-1))][i-1]);  
27 }
28 int query(int x,int y)
29 {
30     int z=floor(log(y-x+1)/log(2));
31     return max(f[x][z],f[y-(1<<z)+1][z])-min(g[x][z],g[y-(1<<z)+1][z]);
32 }
33 int main()
34 {
35     freopen("input.txt","r",stdin);
36     freopen("output.txt","w",stdout);
37     n=read();m=read();
38     for(int i=1;i<=n;i++)a[i]=read();
39     rmq();
40     while(m--)
41     {
42         int x=read(),y=read();
43         printf("%d\n",query(x,y));
44     }
45     return 0;
46 }