[acwing] 58 weeks 4489 Longest subsequence

Preface

$tag:$ thinking
Portal :

The question :
Given a rising Array of , Find a subsequence so that the elements in the subsequence meet $a_j\ast 2\ge a_{j+1}$, Ask about the sequence of legitimate subsequences Maximum length

Ideas :
Because the given array is ascendant

So if $a_1\ast 2\ge a_3$ There is , Then there must be $a_1\ast 2\ge a_2$

Then this condition makes the answer continuity , So we just need $On$ Just sweep it once

code :

#include <iostream>
#include <vector>
#include <map>
#include <cstring>
#include <queue>
#include <math.h>
#include <set>
#include <stack>
#include <algorithm>
using namespace std;
#define IOS ios::sync_with_stdio(false);
#define CIT cin.tie(0);
#define COT cout.tie(0);

#define ll long long
#define x first
#define y second
#define pb push_back
#define endl '\n'
#define all(x) (x).begin(),x.end()
#define Fup(i,a,b) for(int i=a;i<=b;i++)
#define Fde(i,a,b) for(int i=a;i>=b;i--)
#define cer(a) cerr<<#a<<'='<<(a)<<" @ line "<<__LINE__<<" "<<endl
typedef priority_queue<int,vector<int>,greater<int>>  Pri_m;
typedef pair<int,int> pii;
typedef vector<int> VI;
map<int,int> mp;
const int N = 2e5+10,INF = 0x3f3f3f3f;
const double eps = 1e-5;


struct node{
    
    int to,val;
};

int a[N],st[N];

int n,i;

void solve(){
    
	cin>>n;
	int ans = -INF;
	
	Fup(i,1,n) cin>>a[i];
	
	int res =  1;
	
	Fup(i,1,n-1){
    
		if(a[i]*2 >= a[i+1]) res++;
		else res = 1;
		ans = max(ans,res);
		
	}
	cout<<ans<<endl;
	
	
	// Fup(i,1,n-1) if(a[i]*2 >= a[i+1]) st[i] = 1;
	// Fup(i,1,n-1){
    
		// if( !st[i] ) continue;
		// int res = 1;
		// while(st[i]) i ++ , res++;
		// ans = max(res,ans);
	// }
	// if(ans < 0 ) cout<<1<<endl;
	// else cout<<ans<<endl;
	
	
}

int main(){
    
	//int t;cin>>t;while(t--)
    solve();
    return 0 ;
}