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11.2 CountSemiprimes.js
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11.2 CountSemiprimes.js
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function getSieveOfErosthenes(N) {
if (N === 1){
return [false, false];
}
const result = new Array((N/2)+1).fill(true);
for (let i = 2; i < (N+1)/2; i++){
if (result[i]){
for (let j = i*i; j < (N+1)/2; j+=i){
result[j] = false;
}
}
}
return result;
}
function solution(N, P, Q) {
const sieve = getSieveOfErosthenes(N);
const semiprimeCount = new Array(N+1).fill(0);
for (let i = 2; i < (N+1)/2; i++){
if (!sieve[i]){
continue;
}
for (let j = i; i*j <= N; j++){
if (!sieve[j]){
continue;
}
semiprimeCount[i*j] += 1;
}
}
for (let i = 1; i < semiprimeCount.length; i++){
semiprimeCount[i] += semiprimeCount[i-1];
}
const result = [];
for (let i = 0; i < P.length; i++){
result.push(semiprimeCount[Q[i]] - semiprimeCount[P[i]-1])
}
return result;
}