Group Aggregation

Compute the mean of values for each distinct key in keys (a group-by-mean) without using pandas. keys[i] is the group of values[i].

Implement solve(keys, values).

Returns. Return a dict mapping each key to the mean of its values. Keys appear in order of first occurrence.

Examples

Example 1

Input:

solve(['a', 'a', 'b'], [1.0, 2.0, 4.0])

Output:

{'a': 1.5, 'b': 4.0}

Example 2

Input:

solve(['x', 'y', 'x', 'y', 'x'], [10.0, 1.0, 20.0, 3.0, 30.0])

Output:

{'x': 20.0, 'y': 2.0}