单选题库

int partition(vector<int>& arr, int low, int high) {
    int pivot = arr[high]; // 基准值
    int i = low - 1;
 
    for (int j = low; j < high; j++) {
        // 在此处填入代码
    }
    swap(arr[i + 1], arr[high]);
    return i + 1;
}
 
// 快速排序
void quickSort(vector<int>& arr, int low, int high) {
    if (low < high) {
        int pi = partition(arr, low, high);
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}

int factorialA(int n) {
    if (n <= 1) return 1;
    return n * factorialA(n-1);
}
 
int factorialB(int n) {
    if (n <= 1) return 1;
    int res = 1;
    for(int i=2; i<=n; i++)
        res *= i;
}

vector<int> sieve_linear(int n) {
    vector<bool> is_prime(n + 1, true);
    vector<int> primes;
 
    if (n < 2) return primes;
 
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i <= n/2; i++) {
        if (is_prime[i])
            primes.push_back(i);
 
        for (int j = 0; _________________________ ; j++) {  // 在此处填入代码
            is_prime[ i * primes[j] ] = false;
            if (i % primes[j] == 0)
                break;
        }
    }
 
    for (int i = n/2 +1; i <= n; i++) {
        if (is_prime[i])
            primes.push_back(i);
    }
 
    return primes;
}