Cod sursa(job #1316099)

Utilizator alexpetrescuAlexandru Petrescu alexpetrescu Data 13 ianuarie 2015 15:30:02
Problema Pairs Scor 80
Compilator c Status done
Runda Arhiva de probleme Marime 1.21 kb
#include <stdio.h>
#define MAXP 1000000
#define MAXK 7
int e[MAXK], c[MAXP+1];
inline long long gauss(int x){
    return x*(long long)(x+1)/2LL;
}
int main(){
    int n, p, t, i, j, k, div, semn;
    long long ans;
    FILE *fin, *fout;
    fin=fopen("pairs.in", "r");
    fout=fopen("pairs.out", "w");
    fscanf(fin, "%d", &n);
    for(t=0; t<n; t++){
        fscanf(fin, "%d", &p);
        div=2;
        k=0;
        while(div*div<=p){
            if(p%div==0){
                e[k++]=div;
                while(p%div==0){
                    p/=div;
                }
            }
            div++;
        }
        if(p!=1){
            e[k++]=p;
        }
        for(i=1; i<(1<<k); i++){
            p=1;
            semn=1;
            for(j=0; j<k; j++){
                if(((1<<j)&i)!=0){
                    p*=e[j];
                    semn*=-1;
                }
            }
            c[p]+=semn;
        }
    }
    ans=gauss(n-1);
    for(i=2; i<=MAXP; i++){
        if(c[i]<0){
            ans-=gauss(-c[i]-1);
        }else{
            ans+=gauss(c[i]-1);
        }
    }
    fprintf(fout, "%lld\n", ans);
    fclose(fin);
    fclose(fout);
    return 0;
}