多校6047Maximum Sequence

主要是通过那个公式转化成在bk到i之间找最大值，这样就能做了

#include <algorithm>#include <iostream>#include <cstring>#include <cstdlib>#include <vector>#include <cstdio>#include <bitset>#include <cmath>#include <queue>#include <stack>#include <map>#include <set>#define FOR(i,a,b) for(int i=a;i<=b;i++)#define ROF(i,a,b) for(int i=a;i>=b;i--)#define mem(i,a) memset(i,a,sizeof(i))#define rson mid+1,r,rt<<1|1#define lson l,mid,rt<<1#define ll long long#define LL long longusing namespace std;template <typename T>inline void read(T &_x_){    _x_=0;bool f=false;char ch=getchar();    while (ch<'0'||ch>'9') {if (ch=='-') f=!f;ch=getchar();}    while ('0'<=ch&&ch<='9') {_x_=_x_*10+ch-'0';ch=getchar();}    if(f) _x_=-_x_;}const double eps = 1e-8;const int maxn = 5e5+7;const int mod = 1e9+7;const ll inf = 1e15;int n;ll a[maxn],b[maxn];ll sum[maxn];int main(){    while(~scanf("%d",&n)){        memset(sum,0,sizeof(sum));        for(int i=1;i<=n;i++) scanf("%I64d",&a[i]),a[i]-=i;        for(int i=1;i<=n;i++) scanf("%I64d",&b[i]);        sort(b+1,b+n+1);        ll ans=0;        sum[n]=a[n];        for(int i=n-1;i>=1;i--){            sum[i]=max(a[i],sum[i+1]);        }        ll mx = 0;        for(int i=1;i<=n;i++){            ans+=max(mx,sum[b[i]]);            mx=max(mx,sum[b[i]]-n-i);            ans%=mod;        }        printf("%I64d\n",ans);    }    return 0;}