2016夏季练习——ST

来源：POJ3264

用线段树过过一次，用st表来一次

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
int n,Q;
const int MAXN = 50000+10;
int s[MAXN];
long long dp1[MAXN][20];
long long dp2[MAXN][20];
void ini(){
	for(int i=1;i<=n;i++){
		dp1[i][0]=s[i];
		dp2[i][0]=s[i];
	}
	for(int j=1;(1<<j)<=n;j++){
		for(int i=1;i+(1<<j)-1<=n;i++){
			dp1[i][j]=max(dp1[i][j-1],dp1[i+(1<<(j-1))][j-1]);
			dp2[i][j]=min(dp2[i][j-1],dp2[i+(1<<(j-1))][j-1]);
		}
	}
}
int query(int l,int r){
	int dd = (int)(log(double(r-l+1))/(log(2.0)));
	int maxn = max(dp1[l][dd],dp1[1+r-(1<<dd)][dd]);
	int minn = min(dp2[l][dd],dp2[1+r-(1<<dd)][dd]);
	return maxn-minn;
}
int main(){
	int T;
	while(scanf("%d%d",&n,&Q)!=EOF){
		for(int i=1;i<=n;i++){
			scanf("%d",s+i);
		}
		ini();
		int l,r;
		while(Q--){
			scanf("%d%d",&l,&r);
			cout<<query(l,r)<<endl;
		}
	}
	return 0;
}