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1175.cpp
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1175.cpp
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__________________________________________________________________________________________________
sample 0 ms submission
class Solution {
public:
int64_t permutations(int a) {
int64_t result = 1;
for(int64_t i = 2; i <= a; i++) {
result = (result * i) % 1000000007;
}
return result;
}
bool prime(int n) {
if(n <= 1) return false;
if(n <= 3) return true;
for(int i = 2; i <= sqrt(n); i++) {
if(n % i == 0) return false;
}
return true;
}
int numPrimeArrangements(int n) {
int primes = 0;
for(int i = 1; i <= n; i++) {
if (prime(i)) primes++;
}
int64_t a = (permutations(primes) % 1000000007) * (permutations(n - primes) % 1000000007);
return a % 1000000007;
}
};
__________________________________________________________________________________________________
0ms
class Solution {
const int MOD = 1000000000 + 7;
int getPrime(int n){
int num = 0;
for(int i=2;i<=n;i++){
bool is = true;
for(int j=2;j<i;j++){
if(i%j == 0){
is = false;
break;
}
}
if(is)num++;
}
return num;
}
long long jiecheng(int n){
if(n<=1)return 1;
long long ans = 1;
while(n>0){
ans = ans * n % MOD;
n--;
}
return ans;
}
public:
int numPrimeArrangements(int n) {
if(n==1 || n == 2)return 1;
int x = getPrime(n);
return jiecheng(x) * jiecheng(n - x) % MOD;
}
};
__________________________________________________________________________________________________