Sorting array

Sort

 #!/usr/bin/ruby
     # 35 students in our class
     NUM_STUDENTS = 35
     # Max grade of 100%
     MAX_GRADE = 100
     num_compare = 0 
     arr = Array.new(NUM_STUDENTS)
     
     # Randomly populate arr
     for i in 0..(NUM_STUDENTS - 1)
       # Maximum possible grade is 100%, keep in mind that rand(5) returns possible values 0-4, so we must add 1 to MAX_GRADE
       arr[i] = rand(MAX_GRADE + 1)
     end
    
     # Output current values of arr
     puts "Input list:"
     for i in 0..(NUM_STUDENTS - 1)
       puts "arr[" + i.to_s + "] ==> " + arr[i].to_s
     end
    
     # Now let's use a selection sort.
     # We first find the lowest number in the array and then we move it to the beginning of the list
     for i in 0..(NUM_STUDENTS - 2)
       min_pos = i
       for j in (i + 1)..(NUM_STUDENTS - 1)
         num_compare = num_compare + 1
         if (arr[j] < arr[min_pos])
           min_pos = j
         end
       end
       # Now that we know the min, swap it with the current first element (at position i)
       temp = arr[i]
       arr[i] = arr[min_pos]
       arr[min_pos] = temp
     end
    
     # Now output the sorted array
     puts "Sorted list:"
     for i in 0..(NUM_STUDENTS - 1)
       puts "arr[" + i.to_s + "] ==> " + arr[i].to_s
     end
     
     puts "Number of Comparisons ==> " + num_compare.to_s