Gini Impurity

Compute the Gini impurity of a node from its class counts.

Implement solve(counts).

Returns. Return a float in $[0,1)[0,1)$. Counts must be non-negative (otherwise ValueError). A node with no samples at all has impurity 0.0.

Examples

Example 1

Input:

solve([2, 2])

Output:

0.5

Example 2

Input:

solve([5, 0, 0])

Output:

0.0

Example 3

Input:

solve([1, 1, 1, 1])

Output:

0.75