using System;
using System.Collections.Generic;
/*
Print the first 100 prime numbers.
The program is structured for clarity:
- A helper method determines whether a number is prime.
- A generator method collects primes until reaching the desired count.
- Comments explain the reasoning behind each step.
*/
class FirstHundredPrimes
{
/*
Determine whether a number is prime.
The method uses a straightforward and efficient approach:
- Reject numbers below 2.
- Only test divisors up to the square root of the number.
Instead of calling Math.Sqrt repeatedly, we compare i*i <= n
to avoid unnecessary floating‑point work.
*/
private static bool IsPrime(int n)
{
if (n < 2)
return false;
for (int i = 2; i * i <= n; i++) {
if (n % i == 0)
return false; // Found a divisor → not prime
}
return true; // No divisors found → prime
}
/*
Generate a list containing the first `count` prime numbers.
The method increments through natural numbers,
checks primality, and collects primes until the list is full.
*/
private static List<int> FirstNPrimes(int count)
{
var primes = new List<int>(capacity: count);
int number = 2; // Start from the first prime candidate
while (primes.Count < count) {
if (IsPrime(number))
primes.Add(number);
number++;
}
return primes;
}
/*
Compute and print the first 100 prime numbers.
Each prime is printed on its own line.
*/
static void Main()
{
var primes = FirstNPrimes(100);
foreach (var p in primes)
Console.WriteLine(p);
}
}
/*
run:
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
101
103
107
109
113
127
131
137
139
149
151
157
163
167
173
179
181
191
193
197
199
211
223
227
229
233
239
241
251
257
263
269
271
277
281
283
293
307
311
313
317
331
337
347
349
353
359
367
373
379
383
389
397
401
409
419
421
431
433
439
443
449
457
461
463
467
479
487
491
499
503
509
521
523
541
*/
