Solution to challenge 44 task 1 in Raku by Noud

1 files changed, 65 insertions, 0 deletions

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+# Only 100, please.
+#
+# You are given a string “123456789”. Write a script that would insert ”+” or
+# ”-” in between digits so that when you evaluate, the result should be 100.
+
+
+# General calculator that handles + and - using Grammars.
+grammar Calculator {
+    rule TOP {
+        <num>+ %% <op>
+    }
+    token op { '+' | '-' };
+    token num { \d+ }
+}
+
+class Arithm {
+    method TOP($/) {
+        my $res = $<num>[0];
+
+        loop (my $i = 1; $i < $<num>.elems; $i++) {
+            my $num = Int($<num>[$i]);
+            given $<op>[$i - 1] {
+                when '+' { $res += $num; }
+                when '-' { $res -= $num; }
+            }
+        }
+
+        $/.make($res);
+    }
+}
+
+# Subroutine helper that creates all combinations using + and - and uses
+# Calculator grammar to check if the combination adds up to the target value.
+sub _pmcomb($action, @rest, $target) {
+    if (@rest.elems == 0) {
+        my $result = Calculator.parse($action, :actions(Arithm)).made;
+        if ($result == $target) {
+            say $action ~ '=' ~ $result;
+        }
+    } elsif ($action.chars == 0) {
+        _pmcomb(Str(@rest.first), @rest.tail(*-1), $target);
+    } else {
+        _pmcomb($action ~ '+' ~ @rest.first, @rest.tail(*-1), $target);
+        _pmcomb($action ~ '-' ~ @rest.first, @rest.tail(*-1), $target);
+        _pmcomb($action ~ '' ~ @rest.first, @rest.tail(*-1), $target);
+    }
+}
+
+sub pmcomb($str, $n) {
+    _pmcomb('', $str.comb, $n);
+}
+
+sub pmcomb100($str) {
+    pmcomb($str, 100);
+}
+
+
+say "All arithmic combinations of 1234567890 that add up to 100:";
+pmcomb100('1234567890');
+
+say "All arithmic combinations of 1234567890 that add up to 101:";
+pmcomb('1234567890', 101);
+
+say "All arithmic combinations of 1133557799 that add up to 42:";
+pmcomb('1133557799', 42);