[day 4]判断素数_不死心想用day 2优化完成上下界

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//Method_2_Eratosthenes_1.cpp  //判断a到b范围内的素数(包含上下界)  //从小到大扣掉素数的倍数  //Input a,b (正整数)  //Output q,w,e,...(范围内素数,逗号分格,每5个一行)    #include <iostream>  #include <cmath>  using namespace std;  int pow2(int x){//2的x次方int ans = 2;if(x == 0)return 1;for(int i = 1; i < x; i++){ans = ans * 2;}return ans;}int value_1(int x){//下界为偶数return x+pow2(x)+1;}int value_0(int x){//下界为奇数return x+pow2(x);}int main(){  int a,b;cin >> a >> b;//创建数组int length = (b-a+1)/2;bool prime[length];memset(prime,true,sizeof(prime)); //判断对应函数bool flag = 0;if(a%2 == 0)flag = 1;//应用value_1//判断素数   筛选double b_sqrt_2 = sqrt(b)*2;  if(flag == 1){for(int x = 0;value_1(x) < b_sqrt_2 ;x++){int x_value = value_1(x);double temp = sqrt(x_value);        for(int i = 2;i <= temp;i++){              if(x_value%i == 0){                  prime[x]=0;//存在非1非n可整除,非素数                  break;              }          } }for(int j = 0;value_1(j) < b_sqrt_2;j++){  int j_value = value_1(j);            if(prime[j]){                  for(int i = j+j_value; i < length;i = i+j_value){                      prime[i]=0;                  }              }          }  //===========显示============      int judge = 0;//判断换行      for(int x = 0; x < length; x++){          if(prime[x]){  cout << value_1(x) << ',';              judge++;              if(judge%5 == 0)                  cout << endl;  }  }      }else{for(int x = 0;value_0(x) < b_sqrt_2;x++){int x_value = value_0(x);double temp = sqrt(x_value);        for(int i = 2;i <= temp;i++){              if(x_value%i == 0){                  prime[x]=0;//存在非1非n可整除,非素数                  break;              }          } }for(int j = 0;value_0(j) < b_sqrt_2;j++){  int j_value = value_0(j);            if(prime[j]){                  for(int i = j+j_value; i < length;i = i+j_value){                      prime[i]=0;                  }              }          }  //===========显示============      int judge = 0;//判断换行      for(int x = 0; x < length; x++){          if(prime[x]){  cout << value_0(x) << ',';              judge++;              if(judge%5 == 0)                  cout << endl;  }  }  }return 0;}

还没倒腾明白呢....练习几天终于做到写出代码没有错啦~逻辑也觉着自己很正确可惜....显示的数值已经跳出三界还没有来的及找出他们是从哪块石头里蹦出来的....

真是要好好学数学啊啊啊啊啊

今天开始捡起高数!

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