a = [6, 5, 4, 2, 6]

# 1 . continuous integers randomly sorted
# 2. min, max
# 3. missing -> 3
# 4. duplicate -> 6

# similar to this hard LC question
# https://leetcode.com/problems/first-missing-positive/

def detect(l):
  pass

assert detect(a) == (3, 6)



[2,4,5,6,6]=23
[2,3,4,5,6]=17
min=2
max=6



=====
6:2
2:1
5:1
4:1
=====

2,3

sum(keys)=17







min=2
max=6

max-min=4



[1,2,4]
[1,2,3]


min+...+max

expect
2+3+4+5+6
20

actual
23


2+3+4+5+6=20
2+4+5+6+6=23

missing = sum(actual) - sum(expected)
duplicate =