1300. Sum of Mutated Array Closest to Target

class Solution:
    def findBestValue(self, A: List[int], target: int) -> int:
        """ tc O(Nlg(max(A)))  sc O(1)
        find a minimun integer x,  so that sum_at_most(x) == target +-1? 
        x range [0,max(A)]? 
        
        """
        n = len(A)
        def sum_at(x):
            res = 0
            for a in A:
                if a > x:
                    res += x
                else:
                    res += a
            return res 
        l,r = 0,max(A)#10000#target//n, target+1
        while l < r: 
            m =  l + (r-l+1)//2
            # find the max x so that sum of array is smaller than target
            if sum_at(m) <= target:
                l = m 
            else:
                r = m-1 
        # check if (l+1) result a smaller absolute difference
        sum1 = sum_at(l+1)
        sum2 = sum_at(l)
        if abs(sum1-target) >= abs(sum2-target):
            return l # we need to find minimun x if l and l+1 both qualify 
        else:
            return l+1