Length is: '10427'. Missing count: '0' Duplicate count: '424' ##```## # Will return an analysis of the string. # Usage: print analyse( \$string ); sub analyse { # Make an array from the number and create hash. my \$number = shift; my @string = split //, \$number; my %count = (); # Work over the number adding values to the hash. while (1) { my \$candidate = \$string[0].\$string[1].\$string[2].\$string[3]; \$count{\$candidate}++; # Get rid of first element of the array. shift @string; # Break out at the end of array. last if scalar @string < 4; } # Tally up the number of duplicates and missing numbers. my \$duplicates = 0; my \$missing = 0; for ( 0 .. 9999 ) { my \$k = 0 x ( 4 - length \$_ ) . \$_; my \$v = \$count{\$k}; unless ( defined \$v ) { \$missing++; next; } \$duplicates += ( \$v - 1 ) if \$v > 1; } # Create the summary. my \$text; \$text .= " Length is: " . length(\$number) . "\n"; \$text .= " Missing count: " . \$missing . "\n"; \$text .= "Duplicate count: " . \$duplicates . "\n\n"; return \$text; } ```