Cant find what's wrong in the code… Repeat and missing Number

Question

You are given a read only array of n integers from 1 to n.

Each integer appears exactly once except A which appears twice and B which is missing.

Return A and B.

Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Note that in your output A should precede B.

Example:

Input:[3 1 2 5 3] 

Output:[3, 4] 

A = 3, B = 4

My code:

class Solution:
    def repeatedNumber(self, A):
        n=len(A)
        asum=0
        rsum = (n*(n+1))//2
        x=0
        dict={}
        for i in A:
            asum+=A[i]
            
            if A[i] in dict:
                x=A[i]
            else:
                dict[i]=1

        
        diff=rsum-asum
        
        return x,x+diff

>Solution :

Your error is simple, you’re using for i in A: but you refer to i within the for loop as if you did for i in range(len(A)):. To fix this all you need to do is replace all instances of A[i] in your code with i. It should look something like this:

class Solution:
    def repeatedNumber(self, A):
        n=len(A)
        asum=0
        rsum = (n*(n+1))//2
        x=0
        distinct={}
        for i in A:
            asum+=i
            
            if i in distinct:
                x=i
            else:
                distinct[i]=1

        
        diff=rsum-asum
        
        return x,x+diff

I hope that helped:)

Note: It doesn’t have any functional relevance in this case, but it is generally go practice to name your variables something other than the object name. In this case I just renamed the dict variable to distinct, as it also gives readers a better understanding of what the dictionary is actually used for.