Codeforces Round #271 (Div. 2) E question Pillars (line tree maintenance DP ),

Codeforces Round #271 (Div. 2) E question Pillars (line tree maintenance DP ),

Address: http://codeforces.com/contest/474/problem/E

For the first time, we encountered this problem of using a line segment tree to maintain DP. ASC also encountered, at that time it was natural to think of the Line Segment tree to maintain the DP, but there was a simple method for that question, so I did not write it. This time I finally wrote it out ..

The concept of DP is the same as that of finding the longest ascending subsequence. However, when we look for the preceding maximum value, it will time out. Therefore, we can use the line segment tree to maintain this maximum value. Then, because we need to output the path, therefore, we need to use the line segment tree to maintain the position information of each number in the sequence.

After a lot of work, I finally debugged it...

The Code is as follows:

#include <iostream>#include <cstdio>#include <string>#include <cstring>#include <stdlib.h>#include <math.h>#include <ctype.h>#include <queue>#include <map>#include <set>#include <algorithm>using namespace std;#define LL __int64#define lson l, mid, rt<<1#define rson mid+1, r, rt<<1|1const int INF=0x3f3f3f3f;const int MAXN=100000;int maxv[MAXN<<2], cnt, pre[MAXN+10], f[MAXN+10], q_maxp, maxp[MAXN<<2], q_maxv;LL a[MAXN+10], c[MAXN+10], d[MAXN+10];void PushUp(int rt){    maxv[rt]=max(maxv[rt<<1],maxv[rt<<1|1]);    if(maxv[rt<<1]>=maxv[rt<<1|1])        maxp[rt]=maxp[rt<<1];    else        maxp[rt]=maxp[rt<<1|1];}void update(int p, int x, int i, int l, int r, int rt){    if(l==r)    {        maxv[rt]=x;        maxp[rt]=i;        return ;    }    int mid=l+r>>1;    if(p<=mid) update(p,x,i,lson);    else update(p,x,i,rson);    PushUp(rt);}void query(int ll, int rr, int l, int r, int rt){    if(ll<=l&&rr>=r)    {        if(q_maxv<maxv[rt])        {            q_maxv=maxv[rt];            q_maxp=maxp[rt];        }        return ;    }    int mid=l+r>>1, ans=0;    if(ll<=mid) query(ll,rr,lson);    if(rr>mid) query(ll,rr,rson);}int bin_seach(LL x){    int low=0, high=cnt-1, mid;    while(low<=high)    {        mid=low+high>>1;        if(d[mid]==x) return mid;        else if(d[mid]>x) high=mid-1;        else low=mid+1;    }}int l_seach(LL x){    int low=0, high=cnt-1, mid, ans=-1;    while(low<=high)    {        mid=low+high>>1;        if(d[mid]<=x)        {            ans=mid;            low=mid+1;        }        else high=mid-1;    }    return ans;}int r_seach(LL x){    int low=0, high=cnt-1, mid, ans=-1;    while(low<=high)    {        mid=low+high>>1;        if(d[mid]>=x)        {            ans=mid;            high=mid-1;        }        else low=mid+1;    }    return ans;}void print(int x){    if(x==-1) return ;    print(pre[x]);    printf("%d ",x+1);}int main(){    int n, dd, i, x, ans, y, z, max1=-1, pos, tot;    scanf("%d%d",&n,&dd);    for(i=0; i<n; i++)    {        scanf("%I64d",&a[i]);        c[i]=a[i];    }    sort(c,c+n);    d[0]=c[0];    cnt=1;    for(i=1; i<n; i++)    {        if(c[i]!=c[i-1])        {            d[cnt++]=c[i];        }    }    /*for(i=0;i<cnt;i++)    {        printf("%d ",c[i]);    }    puts("");*/    memset(maxv,0,sizeof(maxv));    memset(pre,-1,sizeof(pre));    for(i=0; i<n; i++)    {        x=bin_seach(a[i]);        y=l_seach(a[i]-dd);        z=r_seach(a[i]+dd);        //printf("%d %d %d\n",x,y,z);        q_maxp=-1;        q_maxv=-1;        if(y!=-1)            query(0,y,0,cnt-1,1);        if(z!=-1)            query(z,cnt-1,0,cnt-1,1);        update(x,q_maxv+1,i,0,cnt-1,1);        pre[i]=q_maxp;        if(q_maxv==0)            pre[i]=-1;        if(max1<q_maxv+1)        {            max1=q_maxv+1;            pos=i;        }    }    printf("%d\n",max1);    print(pos);    return 0;}