3Sum Closest

题目描述：
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. You may assume that each input would have exactly one solution.

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).

比3Sum简单，令Math.abs(target-nums[i]-nums[low]-nums[high])最小，然后记录target-nums[i]-nums[low]-nums[high]的值即可。

public int threeSumClosest(int[] nums, int target) {
    Arrays.sort(nums);
    int result=0;
    int min=Integer.MAX_VALUE;
    Set<Integer> set=new HashSet<Integer>();
    for (int i = 0; i < nums.length; i++) {
        if(!set.contains(nums[i])){
            set.add(nums[i]);
            int low=i+1,high=nums.length-1;
            while(low<high){
                int n=Math.abs(target-nums[i]-nums[low]-nums[high]);
                if(n<min){
                    min=n;
                    result=nums[i]+nums[low]+nums[high];
                }
                if(target-nums[i]-nums[low]-nums[high]>0){
                    low++;
                }else{
                    high--;
                }
            }
        }
    }
    return result;
}