CodeForces 675D Tree Construction

Posted 2020-08-09 Fighting Heart

 

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-6;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
template <class T>
inline void read(T &x)
{
    char c=getchar(); x=0;
    while(!isdigit(c)) c=getchar();
    while(isdigit(c)) {x=x*10+c-‘0‘; c=getchar();}
}

const int maxn=100010;
struct X{int x,id;}s[maxn];
int n,sz,ans[maxn],a[maxn];
struct Node { int id,L,R; }node[maxn];

bool cmp(X a,X b){ return a.x<b.x;}
bool cmp1(X a,X b){ return a.id<b.id;}

int dp[maxn][30];
void RMQ_init()
{
    for(int i=0;i<n;i++) dp[i][0]=i;
    for(int j=1;(1<<j)<=n;j++)
        for(int i=0;i+(1<<j)-1<n;i++){
            if(a[dp[i][j-1]]<a[dp[i+(1<<(j-1))][j-1]]) dp[i][j]=dp[i][j-1];
            else dp[i][j]=dp[i+(1<<(j-1))][j-1];
        }
}

int RMQ(int L,int R)
{
    int k=0;
    while((1<<(k+1))<=R-L+1) k++;
    if(a[dp[L][k]]<a[dp[R-(1<<k)+1][k]]) return dp[L][k];
    return dp[R-(1<<k)+1][k];
}

void build(int L,int R,int fa,int f)
{
    int pos=RMQ(L-1,R-1); pos++;
    if(fa!=-1)
    {
        if(f==0) node[fa].L=s[pos].id;
        else node[fa].R=s[pos].id;
    }

    if(pos-1-L>=0) build(L,pos-1,s[pos].id,0);
    if(R-(pos+1)>=0) build(pos+1,R,s[pos].id,1);
}

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%d",&s[i].x),s[i].id=i;
    sort(s+1,s+1+n,cmp);
    for(int i=1;i<=n;i++) a[i-1]=s[i].id;
    RMQ_init(); build(1,n,-1,0);
    sort(s+1,s+1+n,cmp1);
    for(int i=1;i<=n;i++) ans[node[i].L]=s[i].x, ans[node[i].R]=s[i].x;
    for(int i=2;i<=n;i++) printf("%d ",ans[i]);
    return 0;
}