POJ 3264 Balanced Lineup (线段树)

#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;

#define MAXN 50500

struct segTree
{
int minn,maxn;
int l,r;
}tree[MAXN<<3];

void build(int root,int ibegin,int iend)
{
tree[root].l=ibegin;
tree[root].maxn=0;
tree[root].minn=100000000;
tree[root].r=iend;
if(ibegin==iend) return;
int mid=(ibegin+iend)/2;
build(root*2+1,ibegin,mid);
build(root*2+2,mid+1,iend);
}

void update(int root,int laz, int x)
{
if(laz<tree[root].l||laz>tree[root].r)
return ;
if(tree[root].l==tree[root].r)
{
tree[root].maxn=max(tree[root].maxn,x);
tree[root].minn=min(tree[root].minn,x);
return;
}
int mid=(tree[root].l+tree[root].r)/2;
if(laz<=mid) update(root*2+1,laz,x);
else update(root*2+2,laz,x);
tree[root].maxn=max(tree[root*2+1].maxn,tree[root*2+2].maxn);
tree[root].minn=min(tree[root*2+1].minn,tree[root*2+2].minn);
}

int queryminn(int root,int ibegin,int iend)
{
if(iend<tree[root].l||ibegin>tree[root].r)
return -1;
if(tree[root].l==ibegin&&tree[root].r==iend)
return tree[root].minn;
int mid=(tree[root*2+1].l+tree[root*2+2].r)/2;
if(mid<ibegin) return queryminn(root*2+2,ibegin,iend);
else if(iend<=mid) return queryminn(root*2+1,ibegin,iend);
else return min(queryminn(root*2+1,ibegin,mid),
queryminn(root*2+2,mid+1,iend));
}

int querymaxn(int root,int ibegin,int iend)
{
if(iend<tree[root].l||ibegin>tree[root].r)
return -1;
if(tree[root].l==ibegin&&tree[root].r==iend)
return tree[root].maxn;
int mid=(tree[root*2+1].l+tree[root*2+2].r)/2;
if(mid<ibegin) return querymaxn(root*2+2,ibegin,iend);
else if(iend<=mid) return querymaxn(root*2+1,ibegin,iend);
else return max(querymaxn(root*2+1,ibegin,mid),
querymaxn(root*2+2,mid+1,iend));
}

int main()
{
int n,q;int a;
while(cin>>n>>q)
{
build(0,1,n);
for(int i=1;i<=n;i++)
{
scanf("%d",&a);
update(0,i,a);
}
int l,r;
for(int i=1;i<=q;i++)
{
scanf("%d%d",&l,&r);
cout<<querymaxn(0,l,r)-queryminn(0,l,r)<<endl;
}
}
}