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  1. #include <iostream>
  2. #include <cmath>
  3. using namespace std;
  4.  
  5. bool isPrime(int n)
  6. {
  7. 	if (n%2==0) return false;
  8.     for (int i = 3; i <= sqrt(n) + 1; i+=2) { // См. мой комментарий к вопросу
  9.         if (n % i == 0) {
  10.             return false;
  11.         } 
  12.     }
  13.     return true;
  14. }
  15.  
  16. int main() {
  17. for(int n = 2; n < 100; ++n)
  18. cout << n << "    " << (isPrime(n) ? "prime" : "not prime") << endl;
  19.  
  20.  
  21. }
Success #stdin #stdout 0.01s 5400KB
comments (?)
stdin
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Standard input is empty
stdout
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2    not prime
3    prime
4    not prime
5    prime
6    not prime
7    prime
8    not prime
9    not prime
10    not prime
11    prime
12    not prime
13    prime
14    not prime
15    not prime
16    not prime
17    prime
18    not prime
19    prime
20    not prime
21    not prime
22    not prime
23    prime
24    not prime
25    not prime
26    not prime
27    not prime
28    not prime
29    prime
30    not prime
31    prime
32    not prime
33    not prime
34    not prime
35    not prime
36    not prime
37    prime
38    not prime
39    not prime
40    not prime
41    prime
42    not prime
43    prime
44    not prime
45    not prime
46    not prime
47    prime
48    not prime
49    not prime
50    not prime
51    not prime
52    not prime
53    prime
54    not prime
55    not prime
56    not prime
57    not prime
58    not prime
59    prime
60    not prime
61    prime
62    not prime
63    not prime
64    not prime
65    not prime
66    not prime
67    prime
68    not prime
69    not prime
70    not prime
71    prime
72    not prime
73    prime
74    not prime
75    not prime
76    not prime
77    not prime
78    not prime
79    prime
80    not prime
81    not prime
82    not prime
83    prime
84    not prime
85    not prime
86    not prime
87    not prime
88    not prime
89    prime
90    not prime
91    not prime
92    not prime
93    not prime
94    not prime
95    not prime
96    not prime
97    prime
98    not prime
99    not prime
https://ideone.com/mLl7QI
language:
C++14 (gcc 8.3)
created:
1 year ago
visibility:
secret

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