HDU 4521-小明序列（线段树好题）

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cctype>
#include <complex>
#include <cassert>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<int,int> PII;
typedef long long ll;
#define lson l,m,rt<<1
#define pi acos(-1.0)
#define rson m+1,r,rt<<1|1
#define All 1,N,1
#define read freopen("in.txt", "r", stdin)
#define N 100010
const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;
const int INF= 0x7ffffff;
const int mod =  1000000007;
int maxv[N*4],a[N],dp[N];
void pushup(int rt){
    maxv[rt]=max(maxv[rt<<1],maxv[rt<<1|1]);
}
void build(int l,int r,int rt){
    maxv[rt]=0;
    if(l==r){
        return;
    }
    int m=(l+r)>>1;
    build(lson);
    build(rson);
}
void update(int pos,int num,int l,int r,int rt){
    if(l==r){
        maxv[rt]=max(maxv[rt],num);
        return;
    }
    int m=(l+r)>>1;
    if(pos<=m)update(pos,num,lson);
    else update(pos,num,rson);
    pushup(rt);
}
int query(int L,int R,int l,int r,int rt){
    if(L<=l&&R>=r){
        return maxv[rt];
    }
    int m=(l+r)>>1;
    int ans=0;
    if(L<=m)ans=max(ans,query(L,R,lson));
    if(R>m)ans=max(ans,query(L,R,rson));
    return ans;
}
int main()
{
    int n,d;
    while(~scanf("%d%d",&n,&d)){
            int maxl=0;
            for(int i=1;i<=n;++i){
            scanf("%d",&a[i]);
            maxl=max(maxl,a[i]);
            }
        memset(dp,0,sizeof(dp));
        build(0,maxl,1);//以数值做区间
        int maxans=0;
        for(int i=1;i<=n;++i){
            if(i-d-1>0){
                update(a[i-d-1],dp[i-d-1],0,maxl,1);//更新点
            }
            if(a[i]==0){
                dp[i]=1;
            }
            else
            dp[i]=query(0,a[i]-1,0,maxl,1)+1;//查的恰好是值<a[i]且dp[1]---dp[i-d-1]的最大值
            maxans=max(maxans,dp[i]);
        }
        printf("%d\n",maxans);
    }
return 0;
}