3-sum

class Solution:
    # @param A : list of integers
    # @param B : integer
    # @return an integer
    def threeSumClosest(self, A, B):
        A.sort()
        
        if len(A) == 3: 
            return sum(A)
        
        i = 0
        j = 1 
        k = len(A) - 1
        
        def calc(ii=None, jj=None, kk=None):
            return A[ii or i] + A[jj or j] + A[kk or k]
            
        best_result = calc()
        
        def min_(new_result, best_result):
            if abs(new_result - B) < abs(best_result - B):
                return new_result
            return best_result
            
        while True:
            r = calc()
            
            old = [i, j, k]
            
            if best_result == B:
                return best_result
            
            elif r > B:
                while j + 1 < k and calc() >= B:
                    k -= 1
                    best_result = min_(calc(), best_result)
                    
                while j + 1 < k  and calc(jj=j + 1) <= B:
                    j += 1
                    best_result = min_(calc(), best_result)
            else:
                while j + 1 < k and calc(jj=j + 1) <= B:
                    j += 1
                    best_result = min_(calc(), best_result)
                
                while calc() <= B:
                    if i + 1 < j: 
                        i += 1
                    elif j + 1 < k: 
                        j += 1
                    else: 
                        break
                        
                    best_result = min_(calc(), best_result)
                        
                while j - 1 > i and calc(jj=j - 1) >= B:
                    j -= 1
                    best_result = min_(calc(), best_result)

            if old == [i, j, k]: 
                break

        return int(best_result)