ACdream 1216 (ASC training 1) Beautiful People (DP), acdream1216

ACdream 1216 (ASC training 1) Beautiful People (DP), acdream1216

Question address: http://acdream.info/problem? Pid = 1, 1216

At the beginning of this question, we used a line segment tree. Later we found that we still needed DP to process the query, which was quite troublesome .. It will be gone .. Later I thought that this question is actually a two-dimensional longest ascending subsequence ..

Sort first, sort by the first keyword on the left, and then sort by the second keyword on the right. In this case, those with the same first keyword are definitely not in the same ascending subsequence. Then, only perform the DP with the complexity of the second keyword O (n * logn), find the longest ascending sequence, process the precursor, and output 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 long longstruct node{    int x, y, num;}fei[110000];int cmp(node x, node y){    if(x.x==y.x)        return x.y>y.y;    return x.x<y.x;}int a[110000], d[110000], pre[110000], len, b[110000];int bin_seach(int x){    int low=0, high=len, mid, ans;    while(low<=high)    {        mid=low+high>>1;        if(a[mid]>=x)        {            high=mid-1;            ans=mid;        }        else        {            low=mid+1;        }    }    return ans;}int main(){    int n, i, j, pos, cnt;    while(scanf("%d",&n)!=EOF)    {        for(i=0;i<n;i++)        {            scanf("%d%d",&fei[i].x,&fei[i].y);            fei[i].num=i+1;        }        sort(fei,fei+n,cmp);        len=1;        a[1]=fei[0].y;        d[0]=-1;        d[1]=0;        memset(pre,-1,sizeof(pre));        for(i=1;i<n;i++)        {            if(fei[i].y>a[len])            {                a[++len]=fei[i].y;                pre[i]=d[len-1];                d[len]=i;            }            else            {                pos=bin_seach(fei[i].y);                a[pos]=fei[i].y;                pre[i]=d[pos-1];                d[pos]=i;            }        }        printf("%d\n",len);        cnt=0;        /*for(i=0;i<n;i++)        {            printf("%d ",fei[i].num);        }        puts("");*/        for(i=d[len];i!=-1;i=pre[i])        {            b[cnt++]=fei[i].num;            //printf("%d\n",i);        }        for(i=0;i<cnt-1;i++)            printf("%d ",b[i]);        printf("%d\n",b[cnt-1]);    }    return 0;}