Added challenge 17

Author: Steven Landau

challenge_17/README.md

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+Change
+======
+Idea
+-----
+How many ways can you divide 1000 cents into quarters, dimes, nickles and pennies? We're about to find out. Your job today is to create a program which takes an integer from standard input and determines the number of ways that number can be achieved, using the change listed above.
+
+For example, how many ways could we make 100 cents? 
+* 4 Quarters
+* 2 Quarters, 5 Dimes
+* 100 Pennies
+* ...
+
+You must output the number of ways in which change can be given for the input.
+
+Testing
+-----
+100 cents would yield 64207 possible combinations
+
+50 cents would yield 309 possible combinations
+
+150 cents would yield 13322380 possible combinations
+
+I would give more examples but I did it the O(N!) way so it's physically impossible to compute the number of ways to achieve 1000 cents before the universe implodes.

challenge_17/python/slandau3/change.py

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+
+times = 0
+def change(total, p, n, d, q):
+    global times
+    sum = p + n + d + q
+    if sum == total:
+        #print("q:{} d:{} n:{} p:{}".format(q // 25, d // 10, n // 5, p))
+        times += 1
+        return
+    elif sum > total:
+        return
+    else:
+        change(total, p, n, d, q + 25)
+        change(total, p, n, d + 10, q)
+        change(total, p, n + 5, d, q)
+        change(total, total - q - n - d, n, d, q)  # should only have max of 1 depth
+
+change(150, 0, 0, 0, 0)
+print(times)