Merge pull request #1361 from noudald/challenge-050-noud

Solutions to challenge 050 task 1 and 2 in Raku by Noud

2 files changed, 85 insertions, 0 deletions

diff --git a/challenge-050/noud/raku/ch-1.p6 b/challenge-050/noud/raku/ch-1.p6
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+# Merge Intervals
+#
+# Write a script to merge the given intervals where ever possible.
+#
+#     [2,7], [3,9], [10,12], [15,19], [18,22]
+#
+# The script should merge [2, 7] and [3, 9] together to return [2, 9].
+#
+# Similarly it should also merge [15, 19] and [18, 22] together to return [15,
+# 22].
+#
+# The final result should be something like below:
+#
+#     [2, 9], [10, 12], [15, 22]
+#
+
+sub merge-int(@intervals) {
+    if (@intervals.elems < 2) {
+        return @intervals;
+    }
+
+    # Sort intervals ascending.
+    @intervals = @intervals.sort;
+
+    my ($a1, $a2) = @intervals.head;
+    for 1..^@intervals.elems -> $i {
+        if ($a2 < @intervals[$i][0]) {
+            return [($a1, max($a2, @intervals[$i-1][1])),
+                    |(merge-int(@intervals[$i..*]))];
+        }
+    }
+
+    return [($a1, max($a2, @intervals[*-1][1])),];
+}
+
+say merge-int([(2, 3), (-1, 2), (5, 6)]);
+say merge-int([(2, 7), (3, 9), (10, 12), (15, 19), (18, 22)]);
diff --git a/challenge-050/noud/raku/ch-2.p6 b/challenge-050/noud/raku/ch-2.p6
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+# Noble Integer
+#
+# You are given a list, @L, of three or more random integers between 1 and 50.
+# A Noble Integer is an integer N in @L, such that there are exactly N integers
+# greater than N in @L. Output any Noble Integer found in @L, or an empty list
+# if none were found.
+#
+# An interesting question is whether or not there can be multiple Noble
+# Integers in a list.
+#
+# For example,
+#
+# Suppose we have list of 4 integers [2, 6, 1, 3].
+#
+# Here we have 2 in the above list, known as Noble Integer, since there are
+# exactly 2 integers in the list i.e.3 and 6, which are greater than 2.
+#
+# Therefore the script would print 2.
+
+sub noble-int(@L) {
+    return @L.grep(-> $n { @L.grep({ $_ > $n }).elems == $n }).unique;
+}
+
+my @L1 = [2, 6, 1, 3];
+say @L1;
+say noble-int(@L1);
+
+my @L2 = (50.rand.Int for 1..100);
+say @L2;
+say noble-int(@L2);
+
+# An interesting question is whether or not there can be multiple Noble
+# Integers in a list.
+#
+# Answer: Depends on your definition of multiple. For example, the list
+#
+#   [2, 2, 6, 1, 3]
+#
+# contains two Noble integers, 2 and 2. If you exclude non-unique examples I
+# think there are no multiple Noble integers. Suppose there would be a list
+# with multiple (unique) Noble integers. Let N be the smallest Noble integer in
+# the list. I.e. there are N integers larger than N in the list. Let M be
+# another Noble integer in the list. I.e. there are M integers larger than M in
+# the list. All integers larger than M are also larger than N, so the number
+# of integers larger than M is less than N. Hence M < N. But that contradicts
+# the assumption than N was the smallest Noble integer, i.e. we just found a
+# smaller Noble integer than N. Therefore, by contraction, there can only be
+# one (unique) Noble integer in the list.