16. 3Sum Closest(medium)

Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

Example:

Given array nums = [-1, 2, 1, -4], and target = 1.

The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

分析：

从一个整形数组中找出三个数字之和最接近目标值。
和上一个题类似，遍历数组，找到与目标值距离最小的三个数之和。时间复杂度O(n^2)。

Java：

    public int threeSumClosest(int[] nums, int target) {
        Arrays.sort(nums);
        int res = nums[0] + nums[1] + nums[2];
        for (int i = 0; i < nums.length - 2; i++) {
            int lo = i + 1, hi = nums.length - 1;
            while (lo < hi) {
                int sum = nums[i] + nums[lo] + nums[hi];
                if (sum > target) {
                    hi--;
                } else {
                    lo++;
                }
                if (Math.abs(sum - target) < Math.abs(res - target)) {
                    res = sum;
                }
            }
        }
        return res;
    }