Add Python solution to challenge 165

5 files changed, 155 insertions, 7 deletions

diff --git a/challenge-165/paulo-custodio/ch-2.svg b/challenge-165/paulo-custodio/ch-2.svg
index 32091d0113..4e115403f6 100644
--- a/challenge-165/paulo-custodio/ch-2.svg
+++ b/challenge-165/paulo-custodio/ch-2.svg
@@ -49,5 +49,5 @@
 <circle cx="189" cy="154" r="1" stroke="black" />
 <circle cx="361" cy="82" r="1" stroke="black" />
 <circle cx="363" cy="89" r="1" stroke="black" />
-<line x1="0" y1="200.132272535582" x2="500" y2="50.1540224049662" stroke="black" />
+<line x1="0" y1="200" x2="500" y2="50" stroke="black" />
 </svg>
diff --git a/challenge-165/paulo-custodio/perl/ch-1.pl b/challenge-165/paulo-custodio/perl/ch-1.pl
index 116422d124..e35a965a7e 100644
--- a/challenge-165/paulo-custodio/perl/ch-1.pl
+++ b/challenge-165/paulo-custodio/perl/ch-1.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 # Challenge 165
 #
@@ -7,13 +7,13 @@
 #
 # Scalable Vector Graphics (SVG) are not made of pixels, but lines, ellipses,
 # and curves, that can be scaled to any size without any loss of quality. If you
-# have ever tried to resize a small JPG or PNG, you know what I mean by “loss of
-# quality”! What many people do not know about SVG files is, they are simply XML
+# have ever tried to resize a small JPG or PNG, you know what I mean by "loss of
+# quality"! What many people do not know about SVG files is, they are simply XML
 # files, so they can easily be generated programmatically.
 #
-# For this task, you may use external library, such as Perl’s SVG library,
+# For this task, you may use external library, such as Perl's SVG library,
 # maintained in recent years by our very own Mohammad S Anwar. You can instead
-# generate the XML yourself; it’s actually quite simple. The source for the
+# generate the XML yourself; it's actually quite simple. The source for the
 # example image for Task #2 might be instructive.
 #
 # Your task is to accept a series of points and lines in the following format,
diff --git a/challenge-165/paulo-custodio/perl/ch-2.pl b/challenge-165/paulo-custodio/perl/ch-2.pl
index df2d904645..160b7f1a77 100644
--- a/challenge-165/paulo-custodio/perl/ch-2.pl
+++ b/challenge-165/paulo-custodio/perl/ch-2.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 # Challenge 165
 #
@@ -44,6 +44,7 @@ END
 
 sub svg_circle {
     my($cx, $cy, $r)=@_;
+    for($cx, $cy, $r) {$_=int($_);}
     return <<END;
 <circle cx="$cx" cy="$cy" r="$r" stroke="black" />
 END
@@ -56,6 +57,7 @@ sub svg_point {
 
 sub svg_line {
     my($x1,$y1,$x2,$y2)=@_;
+    for($x1,$y1,$x2,$y2) {$_=int($_);}
     return <<END;
 <line x1="$x1" y1="$y1" x2="$x2" y2="$y2" stroke="black" />
 END
diff --git a/challenge-165/paulo-custodio/python/ch-1.py b/challenge-165/paulo-custodio/python/ch-1.py
new file mode 100644
index 0000000000..523e15afe1
--- /dev/null
+++ b/challenge-165/paulo-custodio/python/ch-1.py
@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+
+# Challenge 165
+#
+# Task 1: Scalable Vector Graphics (SVG)
+# Submitted by: Ryan J Thompson
+#
+# Scalable Vector Graphics (SVG) are not made of pixels, but lines, ellipses,
+# and curves, that can be scaled to any size without any loss of quality. If you
+# have ever tried to resize a small JPG or PNG, you know what I mean by "loss of
+# quality"! What many people do not know about SVG files is, they are simply XML
+# files, so they can easily be generated programmatically.
+#
+# For this task, you may use external library, such as Perl's SVG library,
+# maintained in recent years by our very own Mohammad S Anwar. You can instead
+# generate the XML yourself; it's actually quite simple. The source for the
+# example image for Task #2 might be instructive.
+#
+# Your task is to accept a series of points and lines in the following format,
+# one per line, in arbitrary order:
+#
+# Point: x,y
+#
+# Line: x1,y1,x2,y2
+# Example:
+#
+# 53,10
+# 53,10,23,30
+# 23,30
+#
+# Then, generate an SVG file plotting all points, and all lines. If done
+# correctly, you can view the output .svg file in your browser.
+
+def svg_header(width, height):
+    return f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
+<svg height="{height}" width="{width}" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+'''
+
+def svg_footer():
+    return '''</svg>
+'''
+
+def svg_circle(cx, cy, r):
+    return f'<circle cx="{cx}" cy="{cy}" r="{r}" stroke="black" />\n'
+
+def svg_point(cx, cy):
+    return svg_circle(cx, cy, 1)
+
+def svg_line(x1, y1, x2, y2):
+    return f'<line x1="{x1}" y1="{y1}" x2="{x2}" y2="{y2}" stroke="black" />\n'
+
+import sys
+
+file = sys.argv[1] if len(sys.argv) > 1 else None
+if file is None:
+    raise Exception("usage: ch-1.py file.svg")
+
+with open(file, "w") as f:
+    f.write(svg_header(100, 100))
+    for line in sys.stdin:
+        line = line.strip()
+        p = line.split(',')
+        p = [int(coord.strip()) for coord in p]
+        if len(p) == 2:
+            f.write(svg_point(*p))
+        elif len(p) == 4:
+            f.write(svg_line(*p))
+        else:
+            raise Exception(f"cannot parse: {line}")
+    f.write(svg_footer())
diff --git a/challenge-165/paulo-custodio/python/ch-2.py b/challenge-165/paulo-custodio/python/ch-2.py
new file mode 100644
index 0000000000..265da63b9f
--- /dev/null
+++ b/challenge-165/paulo-custodio/python/ch-2.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+
+# Challenge 165
+#
+# Task 2: Line of Best Fit
+# Submitted by: Ryan J Thompson
+#
+# When you have a scatter plot of points, a line of best fit is the line that
+# best describes the relationship between the points, and is very useful in
+# statistics. Otherwise known as linear regression, here is an example of what
+# such a line might look like:
+#
+# Hull
+#
+# The method most often used is known as the least squares method, as it is
+# straightforward and efficient, but you may use any method that generates the
+# correct result.
+#
+# Calculate the line of best fit for the following 48 points:
+#
+# 333,129  39,189 140,156 292,134 393,52  160,166 362,122  13,193
+# 341,104 320,113 109,177 203,152 343,100 225,110  23,186 282,102
+# 284,98  205,133 297,114 292,126 339,112 327,79  253,136  61,169
+# 128,176 346,72  316,103 124,162  65,181 159,137 212,116 337,86
+# 215,136 153,137 390,104 100,180  76,188  77,181  69,195  92,186
+# 275,96  250,147  34,174 213,134 186,129 189,154 361,82  363,89
+
+import sys
+
+def svg_header(width, height):
+    return f'''<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
+<svg height="{height}" width="{width}" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+'''
+
+def svg_footer():
+    return '''</svg>
+'''
+
+def svg_circle(cx, cy, r):
+    return f'<circle cx="{int(cx)}" cy="{int(cy)}" r="{int(r)}" stroke="black" />\n'
+
+def svg_point(cx, cy):
+    return svg_circle(cx, cy, 1)
+
+def svg_line(x1, y1, x2, y2):
+    return f'<line x1="{int(x1)}" y1="{int(y1)}" x2="{int(x2)}" y2="{int(y2)}" stroke="black" />\n'
+
+def least_squares(points):
+    N = len(points)
+    sum_x = sum_y = sum_x2 = sum_xy = 0
+    for x, y in points:
+        sum_x += x
+        sum_y += y
+        sum_x2 += x * x
+        sum_xy += x * y
+    m = (N * sum_xy - sum_x * sum_y) / (N * sum_x2 - sum_x * sum_x)
+    b = (sum_y - m * sum_x) / N
+    return m, b
+
+file = sys.argv[1] if len(sys.argv) > 1 else None
+if file is None:
+    raise Exception("usage: ch-1.py file.svg")
+
+with open(file, "w") as f:
+    f.write(svg_header(500, 500))
+    points = []
+    for line in sys.stdin:
+        for point in line.split():
+            x, y = map(int, point.split(','))
+            points.append((x, y))
+            f.write(svg_point(x, y))
+    m, b = least_squares(points)
+    f.write(svg_line(0, b, 500, m * 500 + b))
+    f.write(svg_footer())