From 103f81c4bf47dad5505081fc6bbf34c770a70f69 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Sun, 24 Mar 2019 19:50:05 -0700
Subject: [PATCH] examples: Add shuffle examples to install list

goodshuffle.py - even shuffle
badshuffle.py - biased shuffle

Signed-off-by: Keith Packard <keithp@keithp.com>
---
 examples/Makefile       |  4 +++-
 examples/badshuffle.py  |  4 +++-
 examples/goodshuffle.py | 26 ++++++++++++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 examples/goodshuffle.py

diff --git a/examples/Makefile b/examples/Makefile
index 48cffa4..369ebf5 100644
--- a/examples/Makefile
+++ b/examples/Makefile
@@ -26,7 +26,9 @@ EXAMPLES = \
 	morse.py \
 	snek-bsd.py \
 	snek.py \
-	track-light.py
+	track-light.py \
+	badshuffle.py \
+	goodshuffle.py
 
 install:
 	install -d "$(DESTDIR)$(EXAMPLEDIR)"
diff --git a/examples/badshuffle.py b/examples/badshuffle.py
index b306a7c..6a36d47 100644
--- a/examples/badshuffle.py
+++ b/examples/badshuffle.py
@@ -2,13 +2,15 @@
 
 import random
 
+random.seed(time.monotonic())
+
 # "Shuffle" a list, but *wrong*.
 
 narray = 16
 a = [0] * narray
 h = [0] * narray
 
-for _ in range(10000):
+for _ in range(100000):
     for i in range(narray):
         a[i] = i
     for i in range(narray):
diff --git a/examples/goodshuffle.py b/examples/goodshuffle.py
new file mode 100644
index 0000000..3863188
--- /dev/null
+++ b/examples/goodshuffle.py
@@ -0,0 +1,26 @@
+#!/usr/bin/python3
+
+import random
+
+random.seed(time.monotonic())
+
+# "Shuffle" a list, but *wrong*.
+
+narray = 16
+a = [0] * narray
+h = [0] * narray
+
+for _ in range(100000):
+    for i in range(narray):
+        a[i] = i
+    for i in range(narray):
+        j = i + random.randrange(narray - i)
+        tmp = a[j]
+        a[j] = a[i]
+        a[i] = tmp
+    for i in range(narray):
+        if a[i] == narray - 1:
+            h[i] += 1
+            break
+
+print(h)