returning to my mutable argument now that i have escaped from borrow hell

(today i learned the important difference between &str and String!)

Signed-off-by: goose.art <did:plc:hsqwcidfez66lwm3gxhfv5in>

day6/src/main.rs

···
 }
 
 impl MathProblem {
-    fn new(nums: Vec<String>) -> MathProblem {
+    fn new(mut nums: Vec<String>) -> MathProblem {
         println!("nums: {:?}", nums);
-        let mut mynums = nums.clone();
-        let operator: char = mynums
+        //let mut mynums = nums.clone();
+        let operator: char = nums
             .pop()
             .expect("Unable to get final char from vector.")
             .chars()
             .next()
             .expect("Operator could not be parsed.");
-        let values: Vec<u64> = mynums.iter().map(|num| num.parse().unwrap()).collect();
+        let values: Vec<u64> = nums.iter().map(|num| num.parse().unwrap()).collect();
         match operator {
             '+' => MathProblem::Sum(values),
             '*' => MathProblem::Mult(values),