暑假集训 7月9日

基础数论：

质数(一般用线性筛)

约数

快速幂

组合数

容斥

补题：

C - Bacteria

救命，取栈顶元素没开long long，太可惜了

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=2e5+10;
priority_queue<ll,vector<ll>,greater<ll> > a;
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin>>n;
    for (int i=0; i<n; i++)
    {
        ll x;
        cin>>x;
        a.push(x);
    }
    int flag=1;
    ll num=0;
    while (a.size()>1)
    {
        ll s=a.top();
        a.pop();
        ll ss=a.top();
        a.pop();
        if (ss==s)
        {
            a.push(ss*2);
        }
        else if (ss!=s)
        {
            if (ss%s==0)
            {
                ll w=s;
                while (w<ss)
                {
                    w*=2;
                    num++;
                }
                if (w==ss)
                {
                    a.push(w*2);
                }
                else
                {
                    flag=0;
                    break;
                }
            }
            else
            {
                flag=0;
                break;
            }
        }
        else
        {
            flag=0;
            break;
        }
    }
    if (!flag)puts("-1");
    else cout<<num<<"\n";
    return 0;
}

 

F - Tickets

 

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e6+10;
int dp[N][30];
int cnt[30];
int judge(int x)
{
    int a=0,b=0;
    int ver=0;
    while (x)
    {
        int w=x%10;
        if (ver<=2)a+=w;
        else b+=w;
        ver++;
        x/=10;
    }
    int c=abs(b-a);
    return c;
}
void cal()
{
    for (int i=0; i<=999999; i++)
    {
        int x=i;
        int c=judge(x);
        cnt[c]++;
        dp[i][c]=cnt[c];
    }
}
signed main()
{
    int n;
    scanf("%d",&n);
    cal();
    while (n--)
    {
        int num;
        scanf("%d",&num);
        int c=judge(num);
        int ans=0;
        for (int i=0; i<c; i++)
        {
            int tmp=num;
            while (dp[tmp][i]==0)tmp--;//没想到，没想到，但是我的方法快了一倍，哈哈哈
            ans+=dp[tmp][i];
        }
        printf("%d\n",ans);
    }
    return 0;
}

 my code：嘿嘿

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e6+10;
int dp[N][30];
int cnt[30];
int judge(int x)
{
    int a=0,b=0;
    int ver=0;
    while (x)
    {
        int w=x%10;
        if (ver<=2)a+=w;
        else b+=w;
        ver++;
        x/=10;
    }
    int c=abs(b-a);
    return c;
}
void cal()
{
    for (int i=0; i<=999999; i++)
    {
        int x=i;
        int c=judge(x);
        cnt[c]++;
        for (int j=0;j<=c;j++)
        {
            dp[i][j]=cnt[j];
        }
    }
}
signed main()
{
    int n;
    scanf("%d",&n);
    cal();
    while (n--)
    {
        int num;
        scanf("%d",&num);
        int c=judge(num);
        ll ans=0;
        for (int i=0; i<c; i++)
        {
            ans+=dp[num][i];
        }
        printf("%d\n",ans);
    }
    return 0;
}