Java
import java.util.ArrayList;
import java.util.Scanner;
/*
* @Description:
* @Version: 2.0
* @Author: xuchaoxin
* @Date: 2021-03-14 21:44:28
* @LastEditors: xuchaoxin
* @LastEditTime: 2021-03-14 21:57:50
*/
public class FilterPrime {
public static void main(String[] args) {
Scanner scanner=new Scanner(System.in);
/*输入素数的上界*/
int n=scanner.nextInt();
scanner.close();
ArrayList<Integer> arrayList = new ArrayList<>();
/* 初始化序列 */
for (int i = 2; i < n; i++) {
arrayList.add(i);
}
int tempPrime;//保存素数
/*开始筛选,初步估计需要二重循环
* 那么要扫描多少次?
* 停止扫描的条件是什么?
* 用while是否更方便?*/
for (int i = 0; i < arrayList.size(); ) {
tempPrime = arrayList.get(0);
System.out.println(tempPrime);
/*注意这里你使用了remove方法*/
/*事实上,当你发现了打印的元素个数不够时,就应该看看打印语句位于哪里,知道去哪里排查问题
* 而不是凭感觉找个地方分析,这往往是我不的不要的习惯*/
for (int j = 0; j < arrayList.size(); j++) {
if (arrayList.get(j) % tempPrime == 0) {
arrayList.remove(j);
}
}
}
}
}
C
#include<stdio.h>
#include<stdlib.h>
int main() {
//另一种策略时数据集抽取,来带到类似产出被筛选的效果,比较消耗空间,但是节省时间
//这里的策略是标记法,比较节省空间,但是耗时间
int n;
printf("input the integer you upper bound you want to print(calculate):\n");
scanf_s("%d", &n);
printf("invoke the malloc function to apply for memory to store integers:\n\
\nin different system may have different sequnce: \n");
int* a = (int*)malloc(n * sizeof(int));//remember to free the memory;
/*if malloc lead to a err ,try use a big enough array to instead.*/
int i1 = 2;//元素序列
int i2 = 0;//索引序列
/*初始换序列2，3，4，5...*/
for (i2 = 0, i1 = 2; i1 < n; ) {
a[i2++] = i1++;
}
/*start to calculate the result*/
//int j = 2/*head element(prime)*/
// , k = 2;/*for traverse*/
//int bi = 0;
int tempPrime=0;
int count = 0;//record how many words have been judged(include nonPrime and konwnPrime)
int index1 = 0;
int index2 = 0;
int index3 = 0;
int line_break = 1;//to help line break counter
for (index1 = 0; count < n; index1++) {
/*扫描第一个非零元素(也就是获取序列的第一个元素(素数))*/
/*打印这个素数*/
for (index2 = 0; index2 < n; index2++) {
if (a[index2]) {
tempPrime = a[index2];
break;
}
}
printf("%-8d\t", tempPrime);//default center right(use '-' to center left)
if (line_break++ % 10 == 0) {
printf("\n");
}
//tempPrime = a[j];
for (index3 = 0; index3 < n; index3++) {
if (a[index3] != 0) {
if (a[index3] % tempPrime == 0) {
a[index3] = 0;
count++;
}
}
}
}
free(a);
}