Add solution 261.

Signed-off-by: Thomas Köhler <jean-luc@picard.franken.de>

1 files changed, 68 insertions, 0 deletions

diff --git a/challenge-261/jeanluc2020/python/ch-2.py b/challenge-261/jeanluc2020/python/ch-2.py
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+++ b/challenge-261/jeanluc2020/python/ch-2.py
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+#!/usr/bin/python3
+# https://theweeklychallenge.org/blog/perl-weekly-challenge-261/#TASK2
+#
+# Task 2: Multiply by Two
+# =======================
+#
+# You are given an array of integers, @ints and an integer $start.
+#
+# Write a script to do the followings:
+#
+# a) Look for $start in the array @ints, if found multiply the number by 2
+# b) If not found stop the process otherwise repeat
+#
+# In the end return the final value.
+#
+## Example 1
+##
+## Input: @ints = (5,3,6,1,12) and $start = 3
+## Output: 24
+##
+## Step 1: 3 is in the array so 3 x 2 = 6
+## Step 2: 6 is in the array so 6 x 2 = 12
+## Step 3: 12 is in the array so 12 x 2 = 24
+##
+## 24 is not found in the array so return 24.
+#
+## Example 2
+##
+## Input: @ints = (1,2,4,3) and $start = 1
+## Output: 8
+##
+## Step 1: 1 is in the array so 1 x 2 = 2
+## Step 2: 2 is in the array so 2 x 2 = 4
+## Step 3: 4 is in the array so 4 x 2 = 8
+##
+## 8 is not found in the array so return 8.
+#
+## Example 3
+##
+## Input: @ints = (5,6,7) and $start = 2
+## Output: 2
+##
+## 2 is not found in the array so return 2.
+#
+############################################################
+##
+## discussion
+##
+############################################################
+#
+# Instead of walking the list for every round, we create a
+# hash with the list elements as keys, which makes the lookup
+# easier. The we just check in a loop whether the current value
+# is still there.
+
+def multiply_by_two(ints: list, start: int) -> None:
+    print("Input: (", ", ".join(str(x) for x in ints), "), ", start, sep="")
+    hash: dict = {}
+    for x in ints:
+        hash[x] = 1
+    while start in hash:
+        start *= 2
+    print(f"Output: {start}")
+
+multiply_by_two( [5,3,6,1,12], 3);
+multiply_by_two( [1,2,4,3], 1);
+multiply_by_two( [5,6,7], 2);
+