Implement and briefly explain the following C$++$ function:

int Sum $($vector nums, int len$)$;

that accepts an integer vector, nums, containing len $>0$ positive integers, and returns

the sum closest to $330$ that was found by adding up to three integers in the vector

$($where each element of the vector can only be included once in the sum$).$

For example, if $[$nums$]$ contains $[101002002]$ and len $==4,$ the function returns

$310,$ since $310=200+100+10.$

If $[$nums$]$ contains $[101002302]$ and len $==4,$ the function returns $330,$ since $330=$

$100+230.$