Merge pull request #42 from mikelane/beginner/#8/sum-earnings

Beginner/#8/sum earnings

beginner/sum_earnings_mikelane.py

@@ -0,0 +1,62 @@
+import functools
+
+
+def sum_earnings(s: str) -> int:
+    """
+    Challenge
+    - Write a function that accepts a comma-separated string input of
+    earning/spending activity and returns the sum of earnings as a
+    single int value.
+
+    - If at any point the spending (negative) value is greater than the
+    sum of earned (positive) values before it then the streak ends and
+    the count should start over
+
+    We have a list in string type separated by commas that represented
+    buy or sell activity. Positive value for selling and negative value
+    for buying activity. For example, in the following string, this
+    user sold something for $7 on the 2nd day, and something for $2 on
+    the 4th day, and then bought something for $12 on the 5th day, and
+    so on.
+
+    >>> sum_earnings('0,7,0,2,-12,3,0,2')
+    5
+
+    This user's highest earnings streak is $5, which started on the 6th
+    day and ended on the 8th day. The streak does not start before the
+    6th day because the user spent $12 on the 5th and broke earlier
+    streak on $9.
+
+    >>> sum_earnings('1,3,-2,1,2')
+    5
+
+    Notes
+    If the user did not do anything (i.e. 0,0,0,0,0) or only bought
+    things without selling anything (i.e. -4,-3,-7,-1), then it should
+    output with 0.
+
+    >>> sum_earnings('0,0,0,0,0')
+    0
+    >>> sum_earnings('-4,-3,-7,-1')
+    0
+
+    Your program should be able to handle a comma-separated string
+    consisting of any number of values. Your program should also be
+    able to handle invalid input. If an invalid input is given, it
+    should output 0.
+
+    some examples of invalid input:
+
+    >>> sum_earnings('qwerty')
+    0
+    >>> sum_earnings(',,3,,4')
+    0
+    >>> sum_earnings('1,2,v,b,3')
+    0
+    """
+    vals = map(int, s.split(','))
+
+    try:
+        return functools.reduce(lambda x, y: max(0, x + y), vals)
+    except ValueError:
+        return 0