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#!/usr/bin/perl -s
use v5.16;
use integer;
use Test2::V0;
use experimental 'signatures';
our ($tests, $examples);
run_tests() if $tests || $examples; # does not return
die <<EOS unless @ARGV;
usage: $0 [-examples] [-tests] [N]
-examples
run the examples from the challenge
-tests
run some tests
N
calculate integer square root of N
EOS
### Input and Output
say int_sqrt(shift);
### Implementation
# Following the formulae in
# https://en.wikipedia.org/wiki/Integer_square_root#Using_only_integer_division
sub int_sqrt ($n) {
my $prev = $n;
while () {
my $next = ($prev + $n / $prev) / 2;
return $prev if $next >= $prev;
$prev = $next;
}
}
### Examples and tests
use Math::Prime::Util ();
sub run_tests {
SKIP: {
skip "examples" unless $examples;
is int_sqrt(10), 3, 'example 1';
is int_sqrt(27), 5, 'example 2';
is int_sqrt(85), 9, 'example 3';
is int_sqrt(101), 10, 'example 4';
}
SKIP: {
skip "tests" unless $tests;
my $mpu_sqrtint = \&Math::Prime::Util::sqrtint;
grep {
int_sqrt($_) != $mpu_sqrtint->($_) and !fail "$_ failed";
} 1 .. 1e5 or pass 'cross check';
}
done_testing;
exit;
}
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