better ideas for arith geo

8b5705bc5d1868d632692e998efc94158dea2cca · ovidiucs · May 8, 2015 01:08
+43 · 1 file changed
medium/07-airth-geo2.py +43 −0
diff --git a/medium/07-airth-geo2.py b/medium/07-airth-geo2.py
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+__author__ = 'mig'
+"""
+Using the Python language, have the function ArithGeoII(arr) take the array of
+numbers stored in arr and return the string "Arithmetic" if the sequence follows
+ an arithmetic pattern or return "Geometric" if it follows a geometric pattern.
+ If the sequence doesn't follow either pattern return -1. An arithmetic sequence
+ is one where the difference between each of the numbers is consistent, where as
+ in a geometric sequence, each term after the first is multiplied by some
+ constant or common ratio. Arithmetic example: [2, 4, 6, 8] and Geometric
+  example: [2, 6, 18, 54]. Negative numbers may be entered as parameters,
+  0 will not be entered, and no array will contain all the same elements.
+"""
+# Input = 5,10,15Output = "Arithmetic"
+# Input = 2,4,16,24Output = -1
+
+def ArithGeoII(arr):
+
+    s = [abs(i) for i in arr]
+    if range(s[0],max(s)+1,s[1] - s[0]) == s:
+        return "Arithmetic"
+    elif is_geometric(s):
+        return "Geometric"
+    return '-1'
+
+def is_geometric(a):
+    # set first test for first element
+    r = a[1]/float(a[0])
+
+    return all(a[i]/float(a[i-1]) == r for i in xrange(2,len(a)))
+
+# keep this function call here
+# to see how to enter arguments in Python scroll down
+print ArithGeoII([3,6,9,12,15])
+print ArithGeoII([2,6,18,54])
+print ArithGeoII([1,5,9])
+print ArithGeoII([-3,-4,-5,-6,-7])
+
+# Basically, it calculates the ratio between the first
+# two, and uses all to determine
+# if all members of the generator are true.
+# Each member of the generator is a boolean value representing
+# whether the ratio between two numbers is equal to the ratio
+# between the first two numbers.