return the only number in the range that is missing from the array-CodePudding

I am trying to use hash table to solve this question. The question description is: "Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array."

My approach so far is to import the dictionary and use it as a list. Then I am enumerating through the integer array that is given to me. So, for now, nums=[0,1,2,3,4,6]. I have to return number 5 as the missing number. After enumerating, I am trying to go over the items of the dictionary and see which number is missing. If the length of the v is none inside the index, then I will return this line int((((length * (length 1))/2) - sums))

 from collections import defaultdict
 class Solution(object):
     def missingNumber(self, nums):
         d = defaultdict(list)
         length = len(nums)
         sums = sum(nums)
         for numbers, index in enumerate(nums):
             d[index].append(numbers)
         
         for k,v in d.items():
             if len(v) == 0 :
                 return int((((length * (length 1))/2) - sums))

I am confused about how to show the if statement. Like how from the list it can be recognized that 5 is missing. Also, if there are more than 2 numbers are missing, then what approach will be the best to take? As if the example was: nums = [0,1,2,6,8]

Pardon for not having enough knowledge. I am just a beginner trying to practice questions everyday.

CodePudding user response：

If you can use sum then no loop is required:

sum1 = sum(nums)
sum2 = sum(range(n))
missing_num = sum2 - sum1

CodePudding user response：

You don't need a dict, you can do it in a for loop

for i in range(n)
    if i not in nums:
        return i

if you are not told what n is then you can do something like:

for i in range(nums[-1])
    if i not in nums:
        return i

if there are a possibility of more than one number missing then you can add them to a list before returning them

missing_nums = []
for i in range(nums[-1]):
    if i not in nums:
        missing_nums.append(i)
return missing_nums