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recursion exercises

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`@@ -41,3 +41,9 @@`
`41`	`41`	`> To design a good algorithm, it is useful to think of the different ways we might define the subproblems that have the same general structure as the original problem.`
`42`	`42`
`43`	`43`	`>Tail recursion - if any recursive call that is made from one context is the very last operation in that context, with the return value of the recursive call immediately returned by enclosing recursion.`
	`44`	`+`
	`45`	`+# Array-Base Sequences`
	`46`	`+> list, tuple and str classes have in common the support of indexing to access individual elements of a sequence, and each uses a low-level concept known as an array to represent that sequence.`
	`47`	`+`
	`48`	`+> * Shallow copy - an array copy of another array that references the same elements as in the first list.`
	`49`	`+> * With`

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	`1`	`+"""Recursive algorithm to find the product of 2 integers m and n using only addition and subtraction"""`
	`2`	`+def productRecursion(n, m):`
	`3`	`+ total=0`
	`4`	`+ if m ==0 or n==0:`
	`5`	`+ return 0`
	`6`	`+ elif m >0 and n>0 :`
	`7`	`+ for _ in range(m):`
	`8`	`+ total+=n`
	`9`	`+ elif (m >0 and n<0):`
	`10`	`+ if n%2==0:`
	`11`	`+ for _ in range(m):`
	`12`	`+ total+=abs(n)`
	`13`	`+ else:`
	`14`	`+ total+=n`
	`15`	`+ elif n>0 and m<0:`
	`16`	`+ if m%2==0:`
	`17`	`+ for _ in range(n):`
	`18`	`+ total+=m`
	`19`	`+ else:`
	`20`	`+ total+=m`
	`21`	`+ elif n<0 and m<0:`
	`22`	`+ for _ in range(abs(m)):`
	`23`	`+ total+=abs(n)`
	`24`	`+ return total`
	`25`	`+`
	`26`	`+print(productRecursion(4,3)) #correct`
	`27`	`+print(productRecursion(3,0)) #correct`
	`28`	`+print(productRecursion(-4,-3))#correct`
	`29`	`+print(productRecursion(3,-4))`
	`30`	`+print(productRecursion(-2,2))#correct`

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	`1`	`+def subsetPrint(list):`
	`2`	`+`
	`3`	`+ #If list is equal to an empty list return the empty list as a sublist (subset)`
	`4`	`+ if list == [] :`
	`5`	`+ return [[]]`
	`6`	`+`
	`7`	`+ """ """`
	`8`	`+ return [[list[0]]+y for y in subsetPrint(list[1:])] +subsetPrint(list[1:])`
	`9`	`+`
	`10`	`+print(subsetPrint([3,2,1]))`
	`11`	`+`
	`12`	`+#Non recursive LeetCode 78`
	`13`	`+`
	`14`	`+def subsets(list):`
	`15`	`+ output=[[]]`
	`16`	`+`
	`17`	`+ for i in list:`
	`18`	`+ output+= [lst + [i] for lst in output]`
	`19`	`+`
	`20`	`+ return output`
	`21`	`+`
	`22`	`+print(subsets([3,2,1]))`

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