注意事项：

  1. i * i 会爆 int，所以在进入循环 for (int j = i * i; j <= n; j += i) 前要先满足 if ((long long)i * i <= m)。

代码：

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bool notpr[MAXn + 10]; int cntpr, pr[MAXn / 10 + 100];
void evapr(int n) {
    notpr[1] = 1;
    for (int i = 2; i <= n; ++i) {
        if (notpr[i] == 0) {
            pr[++cntpr] = i;
            if ((long long)i * i <= n) {
                for (int j = i * i; j <= n; j += i) {
                    notpr[j] = 1;
                }
            }
        }
    }
}

Luogu P3383 【模板】线性筛素数

代码：

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#include<bits/stdc++.h>
using namespace std;
const int MAXn = 1e8;

template <typename T>
inline void read(T &a) {
    char c;for (c = getchar(); (c < '0' || c > '9') && c != '-'; c = getchar());bool f = c == '-';T x = f ? 0 : (c ^ '0');for (c = getchar(); c >= '0' && c <= '9'; c = getchar()) {x = x * 10 + (c ^ '0');}a = f ? -x : x;
}
template <typename T, typename ...Argv>
inline void read(T &a, Argv &...argv) {
    read(a), read(argv...);
}

bool notpr[MAXn + 10]; int cntpr, pr[MAXn / 10 + 100];
void evapr(int n) {
    notpr[1] = 1;
    for (int i = 2; i <= n; ++i) {
        if (notpr[i] == 0) {
            pr[++cntpr] = i;
            if ((long long)i * i <= n) {
                for (int j = i * i; j <= n; j += i) {
                    notpr[j] = 1;
                }
            }
        }
    }
}

int n, m;
signed main() {
    read(n, m);
    evapr(n);
    for (int i = 1, x; i <= m; ++i) {
        read(x);
        printf("%d\n", pr[x]);
    }
    return 0;
}