求每个数的最大质数用埃氏筛法，时间复杂度 O(nlognlogn)
void get_primes(int n) {
for (int i = 2; i <= n; i ++)
if (!st[i]) {
maxp[i] = i;
for (int j = i; j <= n; j += i) {
st[j] = true;
maxp[j] = i;
}
}
}
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只求质数用线性筛法
标签：Code,筛法,nlognlogn,int,质数,数学知识 From： https://www.cnblogs.com/Leocsse/p/16929574.html