Codeforces 447C

447C - DZY Loves Sequences

思路：dp

代码：

#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int INF=0x3f3f3f3f;
const int N=1e5+5;
int a[N];
int f[N],g[N];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin>>n;
    f[1]=1;
    cin>>a[1];
    for(int i=2;i<=n;i++)
    {
        cin>>a[i];
        if(a[i]>a[i-1])f[i]=f[i-1]+1;
        else f[i]=1;
    }
    g[n]=1;
    for(int i=n-1;i>=1;i--)
    {
        if(a[i]<a[i+1])g[i]=g[i+1]+1;
        else g[i]=1;
    }
    int ans=max(g[2]+1,f[n-1]+1);
    for(int i=2;i<n;i++)
    ans=max(ans,max(f[i]+1,g[i]+1));
    for(int i=2;i<n;i++)
    {
        if(a[i+1]>a[i-1]+1)ans=max(ans,f[i-1]+1+g[i+1]);
    }
    cout<<ans<<endl;
    return 0;
}