Pairs with specific difference

class Solution:
    def maxSumPairWithDifferenceLessThanK(self, arr, n, k):
        '''
        We are sorting in decreasing order because we need to findout
        maxpair sum so we will try to pair maxnumber with 2nd max or 3rd max like that
        '''
        arr.sort(reverse=True)
        i,j=0,1
        ans=0
        while i<n:
            #j is in bound
            if j<n:
                #you have found that pair has sum<k
                if arr[i]-arr[j]<k:
                    ans+=arr[i]+arr[j]
                    i,j=i+2,j+2
                #you didnt find j than checking for j+1 is waste since they
                # are in decreasing order.So move to i+1
                else:
                    i=i+1
                    j=i+1
            #j has reached out of bounds so increment i
            else:
                i=i+1
                j=i+1
        return ans