11.15

Posted 2020-11-23 thmyl

https://codeforces.com/gym/102411/problem/M

ICPC 2019-2020 North-Western Russia Regional Contest

 

//A
#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    int a,b,n;
    int x,y,ans=0;
    scanf("%d%d%d",&a,&b,&n);
    x=(n-b)%(b-a);
    y=(n-b)/(b-a);
    if(x)x=3;
    else x=1;
    ans=2*y+x;
    printf("%d
",ans);
    return 0;
}

 

 

//M
//充满魔性的a了一发
#include<iostream>
#include<cstdio>
#include<cstring>
#define maxn 2010
#define mod1 2353733
#define mod2 12377
using namespace std;
int Case,n,a[maxn],b[maxn];
int tim[10000010];
long long ans;
int Hash(int x){
    return (1LL*x*107%mod1+1LL*x*23%mod1+1LL*x*37%mod1)%mod1;
}
int main(){
    scanf("%d",&Case);
    while(Case--){
        memset(tim,0,sizeof(tim));
        ans=0;
        scanf("%d",&n);
        for(int i=1;i<=n;i++){
            scanf("%d",&a[i]);
            b[i]=a[i]*2;
        }
        for(int i=2;i<n;i++){//ö¾ÙÖмäÊýµÄλÖà 
            int hs=Hash(a[i-1]);
            tim[hs]++;
            for(int j=i+1;j<=n;j++){
                if(a[j]<b[i]){
                    int hsnow=Hash(b[i]-a[j]);
                    ans=ans+tim[hsnow];
                }
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}