Merge pull request #4623 from Abigail/abigail/week-123

Abigail/week 123

32 files changed, 873 insertions, 53 deletions

diff --git a/challenge-123/abigail/README.md b/challenge-123/abigail/README.md
index fff6c14deb..e71bda7e0f 100644
--- a/challenge-123/abigail/README.md
+++ b/challenge-123/abigail/README.md
@@ -1,96 +1,84 @@
 # Solutions by Abigail
-## [Average of Stream][task1]
+## [Ugly Numbers][task1]
 
-> You are given a stream of numbers, `@N`.
->
-> Write a script to print the average of the stream at every point.
+> You are given an integer `$n >= 1`.
+> 
+> Write a script to find the $nth element of Ugly Numbers.
+> 
+> > Ugly numbers are those number whose prime factors are `2`, `3` or `5`.
+> > For example, the first 10 Ugly Numbers are `1`, `2`, `3`, `4`, `5`,
+> > `6`, `8`, `9`, `10`, `12`.
 
-### Example
-~~~~
-Input: @N = (10, 20, 30, 40, 50, 60, 70, 80, 90, ...)
-Output:      10, 15, 20, 25, 30, 35, 40, 45, 50, ...
+### Examples
 ~~~~
+Input: $n = 7
+Output: 8
 
-* Average of first number is `10`.
-* Average of first 2 numbers `(10+20)/2 = 15`.
-* Average of first 3 numbers `(10+20+30)/3 = 20`.
-* Average of first 4 numbers `(10+20+30+40)/4 = 25` and so on.
+Input: $n = 10
+Output: 12
+~~~~
 
 ### Solutions
 * [AWK](awk/ch-1.awk)
 * [Bash](bash/ch-1.sh)
-* [Basic](basic/ch-1.bas)
-* [bc](bc/ch-1.bc)
-* [Befunge-93](befunge-93/ch-1.bf)
 * [C](c/ch-1.c)
-* [Go](go/ch-1.go)
-* [Java](java/ch-1.java)
 * [Lua](lua/ch-1.lua)
 * [Node.js](node/ch-1.js)
-* [Pascal](pascal/ch-1.p)
 * [Perl](perl/ch-1.pl)
 * [Python](python/ch-1.py)
 * [R](r/ch-1.r)
 * [Ruby](ruby/ch-1.rb)
-* [Scheme](scheme/ch-1.scm)
-* [Tcl](tcl/ch-1.tcl)
 
 ### Blog
-[Average of Stream][blog1]
+[Perl Weekly Challenge 123: Ugly Numbers][blog1]
 
-## [Basketball Points][task2]
+## [Square Points][task2]
 
-> You are given a score `$S`.
+> You are given coordinates of four points i.e. `(x1, y1)`, `(x2, y2)`,
+> `(x3, y3)` and `(x4, y4)`.
 > 
-> You can win basketball points e.g. `1` point, `2` points and `3` points.
->
-> Write a script to find out the different ways you can score `$S`.
+> Write a script to find out if the given four points form a square.
 
 ### Examples
 ~~~~
-Input: $S = 4
-Output: 1 1 1 1
-        1 1 2
-        1 2 1
-        1 3
-        2 1 1
-        2 2
-        3 1
+Input: x1 = 10, y1 = 20
+       x2 = 20, y2 = 20
+       x3 = 20, y3 = 10
+       x4 = 10, y4 = 10
+Output: 1 as the given coordinates form a square.
 ~~~~
 
 ~~~~
-Input: $S = 5
-Output: 1 1 1 1 1
-        1 1 1 2
-        1 1 2 1
-        1 1 3
-        1 2 1 1
-        1 2 2
-        1 3 1
-        2 1 1 1
-        2 1 2
-        2 2 1
-        2 3
-        3 1 1
-        3 2
+Input: x1 = 12, y1 = 24
+       x2 = 16, y2 = 10
+       x3 = 20, y3 = 12
+       x4 = 18, y4 = 16
+Output: 0 as the given coordinates doesn't form a square.
 ~~~~
 
 ### Solutions
 * [AWK](awk/ch-2.awk)
 * [Bash](bash/ch-2.sh)
+* [bc](bc/ch-2.bc)
 * [C](c/ch-2.c)
+* [Go](go/ch-2.go)
+* [Java](java/ch-2.java)
 * [Lua](lua/ch-2.lua)
 * [Node.js](node/ch-2.js)
+* [Pascal](pascal/ch-2.p)
 * [Perl](perl/ch-2.pl)
 * [Python](python/ch-2.py)
+* [R](r/ch-2.r)
 * [Ruby](ruby/ch-2.rb)
+* [Scheme](scheme/ch-2.scm)
+* [Tcl](tcl/ch-2.tcl)
 
 ### Blog
-[Basketball Points][blog2]
+[Perl Weekly Challenge 123: Square Points][blog2]
 
 
 
-[task1]: https://perlweeklychallenge.org/blog/perl-weekly-challenge-122/#TASK1
-[task1]: https://perlweeklychallenge.org/blog/perl-weekly-challenge-122/#TASK2
-[blog1]: https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-122-1.html
-[blog2]: https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-122-2.html
+[task1]: https://perlweeklychallenge.org/blog/perl-weekly-challenge-123/#TASK1
+[task2]: https://perlweeklychallenge.org/blog/perl-weekly-challenge-123/#TASK2
+[blog1]: https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-123-1.html
+[blog2]: https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-123-2.html
diff --git a/challenge-123/abigail/awk/ch-1.awk b/challenge-123/abigail/awk/ch-1.awk
new file mode 100644
index 0000000000..92040bfcfe
--- /dev/null
+++ b/challenge-123/abigail/awk/ch-1.awk
@@ -0,0 +1,39 @@
+#!/usr/bin/awk
+
+#
+# See ../README.md
+#
+
+#
+# Run as: awk -f ch-1.awk < input-file
+#
+
+BEGIN {
+    ugly [0] = 1
+    next_2   = 0
+    next_3   = 0
+    next_5   = 0
+    count    = 1
+}
+
+{
+    while (count < $1) {
+        c2 = 2 * ugly [next_2]
+        c3 = 3 * ugly [next_3]
+        c5 = 5 * ugly [next_5]
+
+        ugly [count] = c2 < c3 ? c2 < c5 ? c2 : c5 \
+                               : c3 < c5 ? c3 : c5
+
+        if (2 * ugly [next_2] <= ugly [count]) {next_2 ++}
+        if (3 * ugly [next_3] <= ugly [count]) {next_3 ++}
+        if (5 * ugly [next_5] <= ugly [count]) {next_5 ++}
+                                         
+        count ++
+    }
+    print ugly [$1 - 1]
+}
+
+
+
+
diff --git a/challenge-123/abigail/awk/ch-2.awk b/challenge-123/abigail/awk/ch-2.awk
new file mode 100644
index 0000000000..27709d6fd0
--- /dev/null
+++ b/challenge-123/abigail/awk/ch-2.awk
@@ -0,0 +1,20 @@
+#!/usr/bin/awk
+
+#
+# See ../README.md
+#
+
+#
+# Run as: awk -f ch-2.awk < input-file
+#
+
+{
+    e1 = ($1 - $3) ^ 2 + ($2 - $4) ^ 2
+    e2 = ($3 - $5) ^ 2 + ($4 - $6) ^ 2
+    e3 = ($5 - $7) ^ 2 + ($6 - $8) ^ 2
+    e4 = ($7 - $1) ^ 2 + ($8 - $2) ^ 2
+    d1 = ($1 - $5) ^ 2 + ($2 - $6) ^ 2
+    d2 = ($3 - $7) ^ 2 + ($4 - $8) ^ 2
+
+    print ((e1 == e2 && e2 == e3 && e3 == e4 && d1 == d2) ? 1 : 0)
+}
diff --git a/challenge-123/abigail/bash/ch-1.sh b/challenge-123/abigail/bash/ch-1.sh
new file mode 100644
index 0000000000..af24ff46af
--- /dev/null
+++ b/challenge-123/abigail/bash/ch-1.sh
@@ -0,0 +1,37 @@
+#!/bin/sh
+
+#
+# See ../README.md
+#
+
+#
+# Run as: bash ch-1.sh < input-file
+#
+
+set -f
+
+declare -a ugly
+ugly[0]=1
+((next_2 = 0))
+((next_3 = 0))
+((next_5 = 0))
+count=1
+
+while read n
+do  while ((count < n))
+    do  ((c2 = 2 * ${ugly[next_2]}))
+        ((c3 = 3 * ${ugly[next_3]}))
+        ((c5 = 5 * ${ugly[next_5]}))
+
+        if ((c2 <= c3 && c2 <= c5)); then ((ugly[count] = c2)); fi
+        if ((c3 <= c2 && c3 <= c5)); then ((ugly[count] = c3)); fi
+        if ((c5 <= c3 && c5 <= c2)); then ((ugly[count] = c5)); fi
+
+        if ((2 * ${ugly[next_2]} <= ${ugly[count]})); then ((next_2 ++)); fi
+        if ((3 * ${ugly[next_3]} <= ${ugly[count]})); then ((next_3 ++)); fi
+        if ((5 * ${ugly[next_5]} <= ${ugly[count]})); then ((next_5 ++)); fi
+
+        ((count ++))
+    done
+    echo ${ugly[$((n - 1))]}
+done
diff --git a/challenge-123/abigail/bash/ch-2.sh b/challenge-123/abigail/bash/ch-2.sh
new file mode 100644
index 0000000000..fb12779c2e
--- /dev/null
+++ b/challenge-123/abigail/bash/ch-2.sh
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+#
+# See ../README.md
+#
+
+#
+# Run as: bash ch-2.sh < input-file
+#
+
+set -f
+
+while read x1 y1 x2 y2 x3 y3 x4 y4
+do    ((e1 = (x1 - x2) ** 2 + (y1 - y2) ** 2))
+      ((e2 = (x2 - x3) ** 2 + (y2 - y3) ** 2))
+      ((e3 = (x3 - x4) ** 2 + (y3 - y4) ** 2))
+      ((e4 = (x4 - x1) ** 2 + (y4 - y1) ** 2))
+      ((d1 = (x1 - x3) ** 2 + (y1 - y3) ** 2))
+      ((d2 = (x2 - x4) ** 2 + (y2 - y4) ** 2))
+      if ((e1 == e2 && e2 == e3 && e3 == e4 && d1 == d2))
+      then echo 1
+      else echo 0
+      fi
+done
diff --git a/challenge-123/abigail/bc/ch-2.bc b/challenge-123/abigail/bc/ch-2.bc
new file mode 100644
index 0000000000..2ea9169a08
--- /dev/null
+++ b/challenge-123/abigail/bc/ch-2.bc
@@ -0,0 +1,32 @@
+#
+# See ../README.md
+#
+
+#
+# Run as: bc ch-2.bc < input-file
+#
+# Input should be terminated with a line starting with a 0
+#
+
+while (1) {
+    a = read ()
+    if (a == 0) {break}
+    b = read ()
+    c = read ()
+    d = read ()
+    e = read ()
+    f = read ()
+    g = read ()
+    h = read ()
+    i = (a - c) ^ 2 + (b - d) ^ 2
+    j = (c - e) ^ 2 + (d - f) ^ 2
+    k = (e - g) ^ 2 + (f - h) ^ 2
+    l = (g - a) ^ 2 + (h - b) ^ 2
+    m = (a - e) ^ 2 + (b - f) ^ 2
+    n = (c - g) ^ 2 + (d - h) ^ 2
+    o = 0
+    if (i == j && j == k && k == l && m == n) {
+        o = 1
+    }
+    o
+}
diff --git a/challenge-123/abigail/c/ch-1.c b/challenge-123/abigail/c/ch-1.c
new file mode 100644
index 0000000000..cc2f8e54d1
--- /dev/null
+++ b/challenge-123/abigail/c/ch-1.c
@@ -0,0 +1,53 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+
+/*
+ * See ../README.md
+ */
+
+/*
+ * Run as: cc -o ch-1.o ch-1.c; ./ch-1.o < input-file
+ */
+
+typedef long long number;
+int main (void) {
+    int n;
+    number * ugly = NULL;
+    size_t count = 0;
+    size_t next_2, next_3, next_5;
+
+
+    while (scanf ("%d", &n) == 1) {
+        if (n > count) {
+            if ((ugly = (number *) realloc (ugly, n * sizeof (number)))
+                == NULL) {
+                perror ("Realloc failed");
+                exit (1);
+            }
+        }
+        if (count == 0) {
+            ugly [0] = 1;
+            count = 1;
+            next_2 = next_3 = next_5 = 0;
+        }
+        while (count < n) {
+            number c2 = 2 * ugly [next_2];
+            number c3 = 3 * ugly [next_3];
+            number c5 = 5 * ugly [next_5];
+            
+            ugly [count] = c2 < c3 ? c2 < c5 ? c2 : c5
+                                   : c3 < c5 ? c3 : c5;
+
+            if (2 * ugly [next_2] <= ugly [count]) {next_2 ++;}
+            if (3 * ugly [next_3] <= ugly [count]) {next_3 ++;}
+            if (5 * ugly [next_5] <= ugly [count]) {next_5 ++;}
+
+            count ++;
+        }
+        printf ("%lld\n", ugly [n - 1]);
+    }
+    free (ugly);
+
+    return (0);
+}
diff --git a/challenge-123/abigail/c/ch-2.c b/challenge-123/abigail/c/ch-2.c
new file mode 100644
index 0000000000..56f0b615d4
--- /dev/null
+++ b/challenge-123/abigail/c/ch-2.c
@@ -0,0 +1,29 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+
+/*
+ * See ../README.md
+ */
+
+/*
+ * Run as: cc -o ch-2.o ch-2.c; ./ch-2.o < input-file
+ */
+
+int main (void) {
+    int x1, y1, x2, y2, x3, y3, x4, y4;
+
+    while (scanf ("%d %d %d %d %d %d %d %d",
+                   &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4) == 8) {
+        int e1 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
+        int e2 = (x2 - x3) * (x2 - x4) + (y2 - y3) * (y2 - y3);
+        int e3 = (x3 - x4) * (x3 - x4) + (y3 - y4) * (y3 - y4);
+        int e4 = (x4 - x1) * (x4 - x1) + (y4 - y1) * (y4 - y1);
+        int d1 = (x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3);
+        int d2 = (x2 - x4) * (x2 - x4) + (y2 - y4) * (y2 - y4);
+
+        printf ("%d\n", e1 == e2 && e2 == e3 && e3 == e4 && d1 == d2 ? 1 : 0);
+    }
+
+    return (0);
+}
diff --git a/challenge-123/abigail/go/ch-2.go b/challenge-123/abigail/go/ch-2.go
new file mode 100644
index 0000000000..37d275d5dc
--- /dev/null
+++ b/challenge-123/abigail/go/ch-2.go
@@ -0,0 +1,36 @@
+package main
+
+//
+// See ../README.md
+//
+
+//
+// Run as: go run ch-2.go
+//
+
+import (
+    "fmt"
+)
+
+func main () {
+    var x1, y1, x2, y2, x3, y3, x4, y4, e1, e2, e3, e4, d1, d2 int;
+    for {
+        var n, err = fmt . Scanf ("%d %d %d %d %d %d %d %d",
+                                   &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4);
+        if (err != nil || n != 8) {
+            break;
+        }
+        e1 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
+        e2 = (x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3);
+        e3 = (x3 - x4) * (x3 - x4) + (y3 - y4) * (y3 - y4);
+        e4 = (x4 - x1) * (x4 - x1) + (y4 - y1) * (y4 - y1);
+        d1 = (x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3);
+        d2 = (x2 - x4) * (x2 - x4) + (y2 - y4) * (y2 - y4);
+
+        if (e1 == e2 && e2 == e3 && e3 == e4 && d1 == d2) {
+            fmt . Printf ("%d\n", 1);
+        } else { // Seriously, go, else needs to be cuddled?
+            fmt . Printf ("%d\n", 0);
+        }
+    }
+}
diff --git a/challenge-123/abigail/java/ch-2.java b/challenge-123/abigail/java/ch-2.java
new file mode 100644
index 0000000000..8d13bcf8bf
--- /dev/null
+++ b/challenge-123/abigail/java/ch-2.java
@@ -0,0 +1,35 @@
+//
+// See ../README.md
+//
+
+//
+// Run as: ln ch-2.java ch2.java; javac ch2.java; java ch2 < input-file
+//
+
+import java.util.*;
+
+public class ch2 {
+    public static void main (String [] args) {
+        Scanner scanner = new Scanner (System . in);
+        while (scanner . hasNext ()) {
+            int x1 = scanner . nextInt ();
+            int y1 = scanner . nextInt ();
+            int x2 = scanner . nextInt ();
+            int y2 = scanner . nextInt ();
+            int x3 = scanner . nextInt ();
+            int y3 = scanner . nextInt ();
+            int x4 = scanner . nextInt ();
+            int y4 = scanner . nextInt ();
+
+            int e1 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
+            int e2 = (x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3);
+            int e3 = (x3 - x4) * (x3 - x4) + (y3 - y4) * (y3 - y4);
+            int e4 = (x4 - x1) * (x4 - x1) + (y4 - y1) * (y4 - y1);
+            int d1 = (x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3);
+            int d2 = (x2 - x4) * (x2 - x4) + (y2 - y4) * (y2 - y4);
+
+            System . out . println (e1 == e2 && e2 == e3 &&
+                                    e3 == e4 && d1 == d2 ? 1 : 0);
+        }
+    }
+}
diff --git a/challenge-123/abigail/lua/ch-1.lua b/challenge-123/abigail/lua/ch-1.lua
new file mode 100644
index 0000000000..4feb237189
--- /dev/null
+++ b/challenge-123/abigail/lua/ch-1.lua
@@ -0,0 +1,48 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua < input-file
+--
+
+local ugly = {}
+ugly [1] = 1
+local next_2 = 1
+local next_3 = 1
+local next_5 = 1
+local count  = 1
+
+for n in io . lines () do
+    n = tonumber (n)
+    while count < n do
+        local c2 = 2 * ugly [next_2]
+        local c3 = 3 * ugly [next_3]
+        local c5 = 5 * ugly [next_5]
+
+        count = count + 1
+
+        if c2 <= c3 and c2 <= c5 then
+            ugly [count] = c2
+        end
+        if c3 <= c2 and c3 <= c5 then
+            ugly [count] = c3
+        end
+        if c5 <= c2 and c5 <= c3 then
+            ugly [count] = c5
+        end
+
+        if 2 * ugly [next_2] <= ugly [count] then
+            next_2 = next_2 + 1
+        end
+        if 3 * ugly [next_3] <= ugly [count] then
+            next_3 = next_3 + 1
+        end
+        if 5 * ugly [next_5] <= ugly [count] then
+            next_5 = next_5 + 1
+        end
+    end
+    print (ugly [n])
+end
diff --git a/challenge-123/abigail/lua/ch-2.lua b/challenge-123/abigail/lua/ch-2.lua
new file mode 100644
index 0000000000..b379f3078a
--- /dev/null
+++ b/challenge-123/abigail/lua/ch-2.lua
@@ -0,0 +1,30 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-2.lua < input-file
+--
+
+local pat = "(-?%d+)";
+for _ = 2, 8 do
+    pat = pat .. "%s+(-?%d+)";
+end
+
+
+for line in io . lines () do
+    _, _, x1, y1, x2, y2, x3, y3, x4, y4 = line : find (pat)
+    local e1 = (x1 - x2) ^ 2 + (y1 - y2) ^ 2
+    local e2 = (x2 - x3) ^ 2 + (y2 - y3) ^ 2
+    local e3 = (x3 - x4) ^ 2 + (y3 - y4) ^ 2
+    local e4 = (x4 - x1) ^ 2 + (y4 - y1) ^ 2
+    local d1 = (x1 - x3) ^ 2 + (y1 - y3) ^ 2
+    local d2 = (x2 - x4) ^ 2 + (y2 - y4) ^ 2
+    if  e1 == e2 and e2 == e3 and e3 == e4 and d1 == d2 then
+        print (1)
+    else
+        print (0)
+    end
+end
diff --git a/challenge-123/abigail/node/ch-1.js b/challenge-123/abigail/node/ch-1.js
new file mode 100644
index 0000000000..18f9d98e99
--- /dev/null
+++ b/challenge-123/abigail/node/ch-1.js
@@ -0,0 +1,30 @@
+#!/usr/local/bin/node
+
+//
+// See ../README.md
+//
+
+//
+// Run as: node ch-1.js < input-file
+//
+
+let ugly   = [1]
+let next_2 =  0
+let next_3 =  0
+let next_5 =  0
+
+  require ('readline')
+. createInterface ({input: process . stdin})   
+. on              ('line', n => {
+    n =+ n
+    while (ugly . length < n) {
+        ugly . push (Math . min (2 * ugly [next_2], 
+                                 3 * ugly [next_3],
+                                 5 * ugly [next_5]))
+
+        if (2 * ugly [next_2] <= ugly [ugly . length - 1]) {next_2 ++}
+        if (3 * ugly [next_3] <= ugly [ugly . length - 1]) {next_3 ++}
+        if (5 * ugly [next_5] <= ugly [ugly . length - 1]) {next_5 ++}
+    }
+    console . log (ugly [n - 1])
+})
diff --git a/challenge-123/abigail/node/ch-2.js b/challenge-123/abigail/node/ch-2.js
new file mode 100644
index 0000000000..85ec5ce186
--- /dev/null
+++ b/challenge-123/abigail/node/ch-2.js
@@ -0,0 +1,22 @@
+#!/usr/local/bin/node
+
+//
+// See ../README.md
+//
+
+//
+// Run as: node ch-2.js < input-file
+//
+
+  require ('readline')
+. createInterface ({input: process . stdin})   
+. on              ('line', line => {
+    let [x1, y1, x2, y2, x3, y3, x4, y4] = line . split (/ +/) . map (_ => +_)
+    let e1 = (x1 - x2) ** 2 + (y1 - y2) ** 2
+    let e2 = (x2 - x3) ** 2 + (y2 - y3) ** 2
+    let e3 = (x3 - x4) ** 2 + (y3 - y4) ** 2
+    let e4 = (x4 - x1) ** 2 + (y4 - y1) ** 2
+    let d1 = (x1 - x3) ** 2 + (y1 - y3) ** 2
+    let d2 = (x2 - x4) ** 2 + (y2 - y4) ** 2
+    console . log (e1 == e2 && e2 == e3 && e3 == e4 && d1 == d2 ? 1 : 0)
+})
diff --git a/challenge-123/abigail/pascal/ch-2.p b/challenge-123/abigail/pascal/ch-2.p
new file mode 100644
index 0000000000..d71fa1c2f0
--- /dev/null
+++ b/challenge-123/abigail/pascal/ch-2.p
@@ -0,0 +1,31 @@
+Program IsSquare;
+
+(*                  *)
+(* See ../README.md *)
+(*                  *)
+
+(*                                                        *)
+(* Run as: fpc -och-2.out ch-2.p; ./ch-2.out < input-file *)
+(*                                                        *)
+
+var
+    x1, y1, x2, y2, x3, y3, x4, y4: integer;
+    e1, e2, e3, e4, d1, d2: integer;
+
+begin
+    while not eof () do begin
+        readln (x1, y1, x2, y2, x3, y3, x4, y4);
+        e1 := (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
+        e2 := (x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3);
+        e3 := (x3 - x4) * (x3 - x4) + (y3 - y4) * (y3 - y4);
+        e4 := (x4 - x1) * (x4 - x1) + (y4 - y1) * (y4 - y1);
+        d1 := (x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3);
+        d2 := (x2 - x4) * (x2 - x4) + (y2 - y4) * (y2 - y4);
+        if (e1 = e2) and (e2 = e3) and (e3 = e4) and (d1 = d2) then begin
+            writeln (1);
+        end
+        else begin
+            writeln (0);
+        end
+    end
+end.
diff --git a/challenge-123/abigail/perl/ch-1.pl b/challenge-123/abigail/perl/ch-1.pl
new file mode 100644
index 0000000000..83fb0e30ec
--- /dev/null
+++ b/challenge-123/abigail/perl/ch-1.pl
@@ -0,0 +1,58 @@
+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See ../README.md
+#
+
+#
+# Run as: perl ch-1.pl < input-file
+#
+
+use List::Util qw [min];
+my @ugly   = (1);
+my @primes = (2, 3, 5);
+my %next   = map {$_ => 0} @primes;
+
+#
+# We will maintain the following invariants:
+#
+# Foreach $p in @primes:
+#      $p * $ugly [$next {$p} - 1] <= $ugly [-1] < $p * $ugly [$next {$p}]
+#
+# And since every ugly number (except the first) is either twice an
+# ugly number, three times an ugly number, or five times an ugly
+# number, the next ugly number will be the minimum of 
+# (2 * $ugly [$next {2}], 3 * $ugly [$next {3}], 5 * $ugly [$next {5}]).
+#
+# We will spend O(1) time per generated ugly number, so our
+# program will run in O(N) time, using O(N) memory.
+#
+
+while (my $n = <>) {
+    while (@ugly < $n) {
+        #
+        # Calculate the next ugly number.
+        #
+        push @ugly => min map {$_ * $ugly [$next {$_}]} @primes;
+
+        #
+        # Update pointers. It could be that more than one pointer needs
+        # updating. (This happens if the ugly number generated is
+        # divisible by 6, 10, 15, or 30). No pointer ever needs updating twice.
+        #
+        $_ * $ugly [$next {$_}] <= $ugly [-1] and $next {$_} ++ for @primes;
+    }
+    say $ugly [-1];
+}
+
+
+__END__
diff --git a/challenge-123/abigail/perl/ch-2.pl b/challenge-123/abigail/perl/ch-2.pl
new file mode 100644
index 0000000000..7803ed57b0
--- /dev/null
+++ b/challenge-123/abigail/perl/ch-2.pl
@@ -0,0 +1,33 @@
+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See ../README.md
+#
+
+#
+# Run as: perl ch-2.pl < input-file
+#
+# If a quadrilateral has four equal sides, it's a rhombus. 
+# A rhombus in which the diagonals are equal is a square.
+#
+# So we check whether all edges are equal, and whether both diagonals are equal.
+#
+
+while (<>) {
+    my ($x1, $y1, $x2, $y2, $x3, $y3, $x4, $y4) = split;
+    say + ($x1 - $x2) ** 2 + ($y1 - $y2) ** 2 ==
+          ($x2 - $x3) ** 2 + ($y2 - $y3) ** 2 ==
+          ($x3 - $x4) ** 2 + ($y3 - $y4) ** 2 ==
+          ($x4 - $x1) ** 2 + ($y4 - $y1) ** 2 &&
+          ($x1 - $x3) ** 2 + ($y1 - $y3) ** 2 ==
+          ($x2 - $x4) ** 2 + ($y2 - $y4) ** 2 ? 1 : 0
+}
diff --git a/challenge-123/abigail/python/ch-1.py b/challenge-123/abigail/python/ch-1.py
new file mode 100644
index 0000000000..039d236609
--- /dev/null
+++ b/challenge-123/abigail/python/ch-1.py
@@ -0,0 +1,33 @@
+#!/opt/local/bin/python
+
+#
+# See ../README.md
+#
+
+#
+# Run as: python ch-1.py < input-file
+#
+
+import fileinput
+
+ugly   = [1]
+next_2 =  0
+next_3 =  0
+next_5 =  0
+
+
+for n in fileinput . input ():
+    n = int (n)
+    while len (ugly) < n:
+        ugly . append (min ([2 * ugly [next_2],
+                             3 * ugly [next_3],
+                             5 * ugly [next_5]]))
+
+        if 2 * ugly [next_2] <= ugly [-1]:
+            next_2 = next_2 + 1
+        if 3 * ugly [next_3] <= ugly [-1]:
+            next_3 = next_3 + 1
+        if 5 * ugly [next_5] <= ugly [-1]:
+            next_5 = next_5 + 1
+
+    print (ugly [n - 1])
diff --git a/challenge-123/abigail/python/ch-2.py b/challenge-123/abigail/python/ch-2.py
new file mode 100644
index 0000000000..e61a2cc0c5
--- /dev/null
+++ b/challenge-123/abigail/python/ch-2.py
@@ -0,0 +1,25 @@
+#!/opt/local/bin/python
+
+#
+# See ../README.md
+#
+
+#
+# Run as: python ch-2.py < input-file
+#
+
+import fileinput
+
+for line in fileinput . input ():
+    [x1, y1, x2, y2, x3, y3, x4, y4] = \
+         map (lambda x: int (x), line . split (' '))
+    if (x1 - x2) ** 2 + (y1 - y2) ** 2 ==   \
+       (x2 - x3) ** 2 + (y2 - y3) ** 2 ==   \
+       (x3 - x4) ** 2 + (y3 - y4) ** 2 ==   \
+       (x4 - x1) ** 2 + (y4 - y1) ** 2 and  \
+       (x1 - x3) ** 2 + (y1 - y3) ** 2 ==   \
+       (x2 - x4) ** 2 + (y2 - y4) ** 2:
+        print (1)
+    else:
+        print (0)
+        
diff --git a/challenge-123/abigail/r/ch-1.r b/challenge-123/abigail/r/ch-1.r
new file mode 100644
index 0000000000..208c5b4dde
--- /dev/null
+++ b/challenge-123/abigail/r/ch-1.r
@@ -0,0 +1,33 @@
+#
+# See ../README.md
+#
+
+#
+# Run as: Rscript ch-1.r < input-file