2019 NOIP 夏令营（模拟赛1）

一来到夏令营，第一天上机就考试，

哎，简直不让人活了

这难道是给我们的见面礼？？？

A

https://www.luogu.org/problemnew/show/P1197

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string>

using namespace std;

int n,m,q,len=;
int last[],p[],father[],ans[];

struct node
{
    int x;
    int y;
    int next;
} qwq[];

bool bz[];

void add(int x,int y)
{
    qwq[++len].x=x;
    qwq[len].y=y;
    qwq[len].next=last[x];
    last[x]=len;
}

int find(int x)
{
    if(father[x]!=x)
    {
        father[x]=find(father[x]);
    }
    return father[x];
}

int main()
{
    int x,y;
    scanf("%d %d",&n,&m);
    for(int i=;i<=n;i++)
    {
        last[i]=-;
        father[i]=i;
    }
    for(int i=;i<=m;i++)
    {
        scanf("%d %d",&x,&y);
        add(x,y);
        add(y,x);
    }
    scanf("%d",&q);
    for(int i=;i<=q;i++)
    {
        scanf("%d",&p[i]);
        bz[p[i]]=true;
    }
    int tot1=n-q;
    m=m<<;
    for(int i=;i<=m;i++)
    {
        int x=qwq[i].x,y=qwq[i].y,t1=find(x),t2=find(y);
        if(!bz[x]&&!bz[y]&&t1!=t2)
        {
            tot1--;
            father[t1]=t2;
        }
    }
    ans[q+]=tot1;
    for(int k=q;k>=;k--)
    {
        int x=p[k];
        bz[x]=false;
        tot1++;
        for(int i=last[x];i!=-;i=qwq[i].next)
        {
            int t1=find(x),y=qwq[i].y,t2=find(y);
            if(!bz[y]&&t1!=t2)
            {
                tot1--;
                father[t1]=t2;
            }
        }
        ans[k]=tot1;
    }
    for(int i=;i<=q+;i++)
    {
        printf("%d\n",ans[i]);
    }
    return ;
}

　　

---

B

https://www.luogu.org/problemnew/show/CF804B

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;

const int Mod=1e9+;

int main()
{
    string s;
    cin>>s;
    int xx=;
    int sum1=;
    int len=s.length();
    for(int i=len-;i>=;i--)
    {
        if(s[i]=='a')
        {
            sum1=(sum1+xx)%Mod;
            xx=xx*%Mod;
        }
        else if(s[i]=='b')
        {
            xx++;
        }
    }
    cout<<sum1<<endl;
    return ;
}

　　

---

C

https://www.luogu.org/problemnew/show/CF798C

#include<iostream>
#include<cstdio>
#include<cmath>

using namespace std;

int gcd(int x,int y)
{
    if(y==)
    {
        return x;
    }
    else
    {
        return gcd(y,x%y);
    }
}

int a[];

int main()
{
    int n;
    cin>>n;
    for(int i=;i<n;i++)
    {
        cin>>a[i];
    }
    int xx=;
    int ans=;
    int t;
    for(int i=;i<n;i++)
    {
        xx=gcd(xx,a[i]);
    }
    if(xx>)
    {
        cout<<"Yes"<<endl<<""<<endl;
    }
    else
    {
        for(int i=;i<n-;i++)
        {
            while(abs(a[i])%==)
            {
                ans++;
                t=a[i];
                a[i]=a[i]-a[i+];
                a[i+]=t+a[i+];
            }
        }
        while(abs(a[n-])%==)
        {
            ans++;
            t=a[n-];
            a[n-]=a[n-]-a[n-];
            a[n-]=t+a[n-];
        }
        if(ans)
        {
            cout<<"YES"<<endl<<ans<<endl;
        }
        else
        {
            cout<<"NO"<<-<<endl;
        }
    }
    return ;
}