Largest proper divisor of n: Difference between revisions
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The core logic only concerns itself with a list of prime factors; it is never even aware of the original input integer, nor the final integer result. In fact, note that the final multiplication is implicit and never spelled out by the programmer; product is the inverse of factorization, and we requested to work "under" factorization, thus J's algebra knows to apply the inverse of factorization (i.e. taking the product) as the final step.
=={{header|Java}}==
<syntaxhighlight lang="java">
public final class LargestProperDivisor {
public static void main(String[] aArgs) {
for ( int n = 1; n < 101; n++ ) {
System.out.print(String.format("%2d%s", largestProperDivisor(n), ( n % 10 == 0 ? "\n" : " " )));
}
}
private static int largestProperDivisor(int aNumber) {
if ( aNumber < 1 ) {
throw new IllegalArgumentException("Argument must be >= 1: " + aNumber);
}
if ( ( aNumber & 1 ) == 0 ) {
return aNumber >> 1;
}
for ( int p = 3; p * p <= aNumber; p += 2 ) {
if ( aNumber % p == 0 ) {
return aNumber / p;
}
}
return 1;
}
}
</syntaxhighlight>
{{ out }}
<pre>
1 1 1 2 1 3 1 4 3 5
1 6 1 7 5 8 1 9 1 10
7 11 1 12 5 13 9 14 1 15
1 16 11 17 7 18 1 19 13 20
1 21 1 22 15 23 1 24 7 25
17 26 1 27 11 28 19 29 1 30
1 31 21 32 13 33 1 34 23 35
1 36 1 37 25 38 11 39 1 40
27 41 1 42 17 43 29 44 1 45
13 46 31 47 19 48 1 49 33 50
</pre>
=={{header|jq}}==
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