POJ 3264 Balanced Lineup 线段树 单点更新 求区间最值

//POJ 3264 Balanced Lineup 线段树 单点更新 求区间最值
/*
题意：
求区间最大值最小值之差

*/

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

#define INF 100000000
#define N 50005
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r

int n,m;
int big,small;
int mmax[N<<2],mmin[N<<2];

int Max(int x,int y){
return x>y?x:y;
}
int Min(int x,int y){
return x<y?x:y;
}

void Pushup(int rt){
mmax[rt] = Max(mmax[rt<<1],mmax[rt<<1|1]);
mmin[rt] = Min(mmin[rt<<1],mmin[rt<<1|1]);
}

void Build(int rt,int l,int r){
mmax[rt] = -1;
mmin[rt] = INF;
if(l == r)
return;
int mid = (l + r) >> 1;
Build(lson);
Build(rson);
}

void Update(int rt,int l,int r,int x,int val){
if(l == r){
mmax[rt] = Max(mmax[rt],val);
mmin[rt] = Min(mmin[rt],val);
return ;
}
int mid = (l + r) >> 1;
if(x <= mid) Update(lson,x,val);
else		 Update(rson,x,val);
Pushup(rt);
}

void Query(int rt,int l,int r,int L,int R){
if(L <= l && R >= r){
big = Max(big,mmax[rt]);
small = Min(small,mmin[rt]);
return;
}
int mid = (l + r) >> 1;
if(L <= mid) Query(lson,L,R);
if(R > mid ) Query(rson,L,R);
}

int main(){
int i,x;
int a,b;
while(scanf("%d %d",&n,&m)!=EOF){
Build(1,1,n);
for(i = 1; i <= n; ++i){
scanf("%d",&x);
Update(1,1,n,i,x);
}
for(i = 1; i <= m; ++i){
scanf("%d %d",&a,&b);
big = -1;small = INF;
Query(1,1,n,a,b);
printf("%d\n",big-small);
}
}
return 0;
}