CodeForces 722C Destroying Array

并查集，离线操作。

将操作倒着进行，一开始所有数字都没有加入到数组中，然后倒着一个一个加入，更新最大值。

#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;
int n;
LL a[maxn],sum[maxn],ans[maxn];
int b[maxn],f[maxn],fa[maxn];

int Find(int x)
{
    if(x!=fa[x]) fa[x]=Find(fa[x]);
    return fa[x];
}

void work(int a,int b)
{
    if(b<=0||b>n) return;
    if(f[b]==0) return;
    int ga=Find(a),gb=Find(b);
    if(ga!=gb)
    {
        fa[gb]=ga;
        sum[ga]=sum[ga]+sum[gb];
        sum[gb]=0;
    }
}

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++) fa[i]=i;
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=n;i++) cin>>b[i];
    for(int i=1;i<=n;i++) sum[i]=a[i];
    LL mx=0;
    for(int i=n;i>=1;i--)
    {
        ans[i]=mx; f[b[i]]=1;
        work(b[i],b[i]-1);
        work(b[i],b[i]+1);
        mx=max(mx,sum[b[i]]);
    }
    for(int i=1;i<=n;i++) cout<<ans[i]<<endl;
    return 0;
}