3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers.

Example

For example, given array S = [-1 2 1 -4], and target = 1. The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

Solution

to compare the closest , do abs(sum - target) ,

don't do sum == target check instead of <=

dont' do duplicate check.

class Solution:
    """
    @param numbers: Give an array numbers of n integer
    @param target : An integer
    @return : return the sum of the three integers, the sum closest target.
    """
    def threeSumClosest(self, numbers, target):
        numbers.sort()
        ans = None
        for i in range(len(numbers) - 2):
            l, r = i + 1, len(numbers) - 1
            while (l < r):                    
                sum = numbers[l] + numbers[r] + numbers[i]
                if ans is None or abs(sum- target) < abs(ans - target):
                    ans = sum
                if sum <= target:
                    l = l + 1
                else:
                    r = r - 1
        return ans