16. 3Sum Closest

public class Solution {
    public int threeSumClosest(int[] num, int target) {
        if(num == null || num.length<3)
            return 0;
        
        Arrays.sort(num);
        int closest = num[0]+num[1]+num[2];
        for(int first = 0;first<num.length-2;++first)
        {
            if(first > 0 && num[first]==num[first-1])
                continue;
            
            int second = first+1;
            int third = num.length -1;
            
            while(second<third)
            {
                int sum = num[first]+num[second]+num[third]; 
                if(sum == target)
                    return target; 
                if(sum>target)
                    --third;
                else 
                    ++second;
                if(Math.abs(closest-target)>Math.abs(sum-target))
                   closest = sum;
            }
            
        }
        
        return closest;
    }
}