POJ 1631 Bridging signals

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

const int maxn=40000+10;
int dp[maxn];
int a[maxn];
int T,n,ans,f;
struct SegTree
{
int MAX;
}s[4*maxn];

void pushUp(int rt)
{
s[rt].MAX=max(s[2*rt].MAX,s[2*rt+1].MAX);
}

void build(int l,int r,int rt)
{
s[rt].MAX=0;
if(l==r) return;
int m=(l+r)/2;
build(l,m,2*rt);
build(m+1,r,2*rt+1);
}

void update(int pos,int val,int l,int r,int rt)
{
if(l==r)
{
s[rt].MAX=val;
return;
}

int m=(l+r)/2;
if(pos<=m) update(pos,val,l,m,2*rt);
else update(pos,val,m+1,r,2*rt+1);
pushUp(rt);
}

void quary(int L,int R,int l,int r,int rt)
{
if(L<=l&&r<=R)
{
f=max(f,s[rt].MAX);
return;
}

int m=(l+r)/2;
if(L<=m) quary(L,R,l,m,2*rt);
if(R>m) quary(L,R,m+1,r,2*rt+1);
}

int main()
{
//   freopen("test.in","r",stdin);
//   freopen("test.out","w",stdout);

scanf("%d",&T);
while(T--)
{
scanf("%d",&n); ans=0;
for(int i=1;i<=n;i++) scanf("%d",&a[i]);
build(1,n,1);
for(int i=1;i<=n;i++)
{
f=0;
if(a[i]==1) f=0;
else quary(1,a[i]-1,1,n,1);
dp[i]=f+1;
update(a[i],dp[i],1,n,1);
ans=max(ans,dp[i]);
}
printf("%d\n",ans);
}
return 0;
}