Float numbers and operators - Feb. 14, 2018 mock interview 10:00 pm

Float number and operators mock interview Feb 14 2018

Given a list of float numbers, and four operators +, -, *, / with flat preference, find the maximum 
value by inserting operator between each consecutive pair of numbers.

For example, given the array [1, 12, -3], the maximum number 33 can be found using 1 - 12 * (-3), since
all operators have flat preference, so 1 - 12 * (-3) will be handled from left to right, first operation 
is 1 - 12 with value -11, and then second operation is -11 * (-3) = 33.
 

      +  -   *  /
  1  1?   1
  12 12  -12
  -3 9    10
  
  1, 12, -3 
  
Julia gave the hint:  
  First two number
  1 + 12  = 13
  1 - 12  = - 11
  1 /12  = 1/12
  1 * 12 = 12
  
  The result first two number, brute force way, work with -3 
  [13, -3]  -> another four options
  
  [-11, -3] -> 
  
  [1/12. -3]->
  
  [12, -3] ->
  
  4 * 4 = 16  
What should we do to reduce the problem space? Save four numbers, or three numbers or two numbers 
or one number?

The interviewee took the hint, and decided to save max and min; and he started to write the optimal 
solution. 

int computeMax(int[] arr, char[] ops) {
    int acc = arr[0];
  
    Integer max = acc;
    Integer min = acc;
    for (int i = 1; i < arr.length; i++) {
      int operand = arr[i];
      
      int tmpMax = max;
      int tmpMin = min; 
      for (char op : ops) {
        int result1 = performOp(op, tmpMax, operand);
        int result2 = performOp(op, tmpMin, operand);
        
        max = Math.max(result1, result2);
        min = Math.min(result1, result2);
      }
    }
  
  return Math.max(max, min);
}