LightOJ 1336 Sigma Function(1--n中所有因子和为偶数的数字个数)

const int MAX_N = 10010;

int prime_cnt, total;
int prime[MAX_N], sum[MAX_N], Left[MAX_N];
bitset<MAX_N> bs;

void GetPrime()
{
prime_cnt = 0;
bs.set();
for(int i = 2; i < MAX_N; i++){
if(bs[i]) prime[prime_cnt++] = i;
for(int j = 0; j < prime_cnt && i * prime[j] < MAX_N; j++){
bs[i * prime[j]] = 0;
if(i % prime[j] == 0) break;
}
}
}

bool Judge(int x)
{
for(int i = 0; prime[i] * prime[i] <= x; i++){
if(x % prime[i] == 0){
int num = 0;
while(x % prime[i] == 0){
num++;
x /= prime[i];
}
if(prime[i] != 2 && (num & 1)) return true;
}
}
if(x > 2) return true;
return false;
}

int main()
{
GetPrime();
total = 0;
for(int i = 1; i < MAX_N; i++){
if(!Judge(i)) Left[total++] = i;;
}
for(int i = 0;  i < total; i++){ //Left数组存的就是因子和为奇数的数
printf("%4d ", Left[i]);
if((i + 1) % 10 == 0) printf("\n");
}
}

#include <stdio.h>
#include <algorithm>
using namespace std;
typedef long long ll;
const int MAX_N = 1000010;

int T, cases = 0;
ll n;

int main()
{
scanf("%d", &T);
while(T--){
scanf("%lld", &n);
ll num = 0;
for(ll i = 1; i * i <= n; i++){
num++;
if( 2 * i * i <= n) num++;
}
printf("Case %d: %lld\n", ++cases, n - num);
}
return 0;
}