+ 1

Have I done this code in right way? Is there another possible easy way to find a prime number?

https://code.sololearn.com/c9BqIEjuIFQH/?ref=app

10th Aug 2019, 8:11 PM
Plaban Kr. Mondal
Plaban Kr. Mondal - avatar
2 odpowiedzi
+ 6
Your algorithm does not work correctly, because every odd number is identified as prime number. This is caused by two mistakes: 1. You use the decrement operator in the range: var x = 2..inputNum-- this will modify the input-value off an odd number to an even number. Change it to: var x =2..(inputNum-1) (by the way: it would be sufficient to have a range from 2 to the square root of the input-number. For example, if you want to test 101 for prime, your test-range needs only to be 2..10) 2. Your if-condition is not correct. A number is prime if there is a remainder for all numbers in the given range! But in your code a division without a remainder would be a criterion for being prime. A modification could be: if (inputNum % a ==0){ println("given number is not a prime number") break } and the else-statement must be removed, because a number is only prime, if ALL remainders are greater then zero. So you have to wait until the loop is complete, before you can make a decision about being prime. This looks differently for the opposite decision: you can immediately break the loop, if a remainder of zero is found.
10th Aug 2019, 10:23 PM
Michael
Michael - avatar
+ 1
Thanks Michael.. greatly appreciate your help
10th Aug 2019, 10:28 PM
Plaban Kr. Mondal
Plaban Kr. Mondal - avatar