Codeforces 446A DZY Loves Sequences

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动态规划

求出l[i] 满足a[i-l[i]+1]<a[i-l[i]+2]<...<a[i]

求出r[i] 满足a[i]<a[i+1]<...<a[i+r[i]-1]

a[i+1]>a[i-1]+1 更新ans=max(ans,l[i-1]+1+r[i+1])

否则更新ans=max(ans,l[i-1]+1,r[i+1]+1)

#include<bits/stdc++.h>using namespace std;int a[100020],l[100020],r[100020];int main(){    int n;    scanf("%d",&n);    for(int i=1;i<=n;i++)        scanf("%d",&a[i]);    l[1]=1,r[n]=1;    for(int i=2;i<=n;i++)    {        if(a[i]>a[i-1])            l[i]=l[i-1]+1;        else            l[i]=1;    }    for(int i=n-1;i>=1;i--)    {        if(a[i]<a[i+1])            r[i]=r[i+1]+1;        else            r[i]=1;    }    int ans=0;    for(int i=1;i<=n;i++)    {        if(a[i+1]>a[i-1]+1)        {            if(l[i-1]+1+r[i+1]>ans)                ans=l[i-1]+1+r[i+1];        }        else        {            if(l[i-1]+1>ans)                ans=l[i-1]+1;            if(r[i+1]+1>ans)                ans=r[i+1]+1;        }    }    printf("%d\n",ans);    return 0;}

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