Support Counting

Compute the support of an itemset: the fraction of transactions that contain every item of the itemset. Items inside a transaction are treated as a set.

Implement solve(transactions,itemset).

Returns. Return a float in $[0,1][0,1]$. The empty itemset is contained in every transaction, so its support is 1.0. There must be at least one transaction.

Examples

Example 1

Input:

solve([['a', 'b'], ['a', 'c'], ['a', 'b']], ['a', 'b'])

Output:

0.666667

Example 2

Input:

solve([['a', 'b'], ['a', 'c'], ['a', 'b']], ['c'])

Output:

0.333333