POJ 3264Balanced Lineup

题意：线段树水题，区间取最大值最小值即可，不用更新，直接跑；

#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<set>
#include<vector>
#include<stack>
#define N 50005
#define INF 0x3f3f3f3f
using namespace std;
typedef struct node{
	int x;int y;int M;int m; 
}node;
node a[N*4];
int b[N];
void built(int root,int first,int end){
	if(first==end){
		a[root].x=first;a[root].y=end;a[root].m=b[first];a[root].M=b[first];
		return ;
	}
	int mid=(first+end)/2;
	built(root*2,first,mid);
	built(root*2+1,mid+1,end);
  a[root].x=a[root*2].x;a[root].y=a[root*2+1].y;a[root].m=min(a[root*2].m,a[root*2+1].m);
  a[root].M=max(a[root*2].M,a[root*2+1].M);
}
int sum,ans;
void U(int root,int first,int end,int l,int r){
	if(l<=first&&end<=r){
		sum=min(sum,a[root].m);
		ans=max(ans,a[root].M);
		return ;
	}
	int mid=(first+end)/2;
	if(l<=mid)  U(root*2,first,mid,l,r);
	if(r>mid)  U(root*2+1,mid+1,end,l,r);
}
int main(){
	int n,q;
	scanf("%d %d",&n,&q);
	for(int i=1;i<=n;i++){
		scanf("%d",&b[i]);
	}
	built(1,1,n);
	int c,d;
	for(int i=1;i<=q;i++){
		scanf("%d %d",&c,&d);
		sum=INF;
		ans=-INF;
		U(1,1,n,c,d);
		printf("%d
",ans-sum);
	}
	return 0;
}