Codeforces Round #561 (Div. 2)

Codeforces Round #561 (Div. 2)

A

# include <bits/stdc++.h>
using namespace std;
​
int f[30];
int main()
{
    int n;
    string name;
    
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        cin>>name;
        f[name[0]-'a']++;
        //cout<<name<<endl;
    }
    int maxx=0;
    
    int c,y;
    int a,b=0;
    for(int i=0;i<26;i++){
        c=f[i]/2;
        y=f[i]%2;
        a=c+y;
        for(int i=1;i<c;i++){
            b+=i;
        }
        for(int i=1;i<a;i++){
            b+=i;
        }
        //cout<<c<<" "<<a<<endl;
    }
    
    printf("%d",b);
    
    return 0;
 } 
​

B

# include <bits/stdc++.h>
using namespace std;
​
​
int main()
{
    int k;
    scanf("%d",&k);
    
    if(k<25){
        printf("-1");
    }else{
        char a[5][5]={{'a','e','i','o','u'},
                      {'e','i','o','u','a'},
                      {'i','o','u','a','e'},
                      {'o','u','a','e','i'},
                      {'u','a','e','i','o'}};
        int n,m;
        int flag=0;
        for(int i=5;i<=(k/5);i++){
            if(k%i==0){
                n=i;
                m=k/i;
                flag=1;
                break;
            }
        }
        if(flag==0) printf("-1");
        else{
            for(int i=0;i<5;i++){
                for(int j=0;j<5;j++){
                    printf("%c",a[i][j]);
                }
                for(int j=5;j<m;j++){
                    if(i==0) printf("a");
                    else if(i==1) printf("e");
                    else if(i==2) printf("i");
                    else if(i==3) printf("o");
                    else if(i==4) printf("u");
                }
            }
            for(int i=5;i<n;i++){
                printf("aeiou");
                for(int j=5;j<m;j++){
                    printf("a");
                }
            }
        }
    }
    
    return 0;
}
​

C

# include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL MANX=2e5+10;
LL sum=0;
vector<LL> a;
int main()
{
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        LL x;
        scanf("%lld",&x);
        x=abs(x);
        a.push_back(x);
    }
    sort(a.begin(),a.end());
    for(int i=0;i<n;i++){
        vector<LL>::iterator it;
        it=upper_bound(a.begin(),a.end(),a[i]*2);
        sum+=(it-(a.begin()+i)-1);
    }
    
    printf("%lld",sum);
    return 0;
}
​