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  1. #include <cstdlib>
  2. #include <iostream>
  3. using namespace std;
  4. int sqrt(int n)//對<1000000的正整數開根號到整數位
  5. {
  6.     int i=0,j=0,k=0;
  7.     int div[3],quot[3],ans;
  8.     div[0]=n/10000;
  9.     div[1]=(n%10000)/100;
  10.     div[2]=n%100;
  11.     while(i*i<=div[0]) i++;
  12.     i--;
  13.     quot[0]=i;//ans的百位數
  14.     div[1]=div[1]+(div[0]-i*i)*100;
  15.     i*=20;
  16.     while(i*j<=div[1])
  17.     {
  18.         j++; i++;
  19.     }
  20.     i--; j--;
  21.     quot[1]=j;//ans的十位數
  22.     div[2]=div[2]+(div[1]-i*j)*100;
  23.     i=(i+j)*10;
  24.     while(i*k<=div[2])
  25.     {
  26.         i++; k++;
  27.     }
  28.     i--; k--;
  29.     quot[2]=k;//ans的個位數
  30.     ans=quot[0]*100+quot[1]*10+quot[2];
  31.     return ans;
  32. }
  33. int check_prim(int p,int n)//n為sqrt(p)，p為input
  34. {
  35.     int i;
  36.     while (p%2!=0)
  37.     {
  38.         for(i=3;i<=n;i+=2)
  39.         {
  40.             if(p%i==0) return 0;
  41.         }
  42.         return 1;
  43.     }
  44.     return 0;
  45. }
  46. int main()
  47. {
  48.     int pri,n;
  49.     cout << "請輸入一個整數<1000000，判斷是否為質數?" << endl;
  50.     cin >> pri;
  51.     n=sqrt(pri);
  52.     cout << "開根號至整數為:" << endl << n << endl;
  53.     if (check_prim(pri,n)) 
  54.         cout << pri << "為質數" << endl;
  55.     else
  56.         cout << pri << "不為質數" << endl; 
  57.     system("pause");
  58. }
  59.  
Success #stdin #stdout 0.01s 5268KB
comments (?)
stdin
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8100
stdout
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請輸入一個整數<1000000，判斷是否為質數?
開根號至整數為:
90
8100不為質數
https://ideone.com/GD24u
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
secret

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