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例如，给定数组 nums = [-1，2，1，-4], 和 target = 1.

与 target 最接近的三个数的和为 2. (-1 + 2 + 1 = 2).

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struct Solution;

// @lc code=start
impl Solution {
    /// ## 解题思路
    /// - 双指针
    /// 1. 类似15.三数和的思路
    pub fn three_sum_closest(nums: Vec<i32>, target: i32) -> i32 {
        //
        let len = nums.len();
        if len < 3 {
            return 0;
        }

        let mut nums = nums;
        nums.sort();
        let mut res = None;
        let mut diff = i32::MAX;

        let c_diff = |sum, target| -> i32 { (sum as i32 - target as i32).abs() };
        'outer: for i in 0..len - 2 {
            let (mut l, mut r) = (i + 1, len - 1);
            while l < r {
                let sum = nums[i] + nums[l] + nums[r];
                if c_diff(sum, target) < diff {
                    diff = c_diff(sum, target);
                    res = Some(sum);
                    if diff == 0 {
                        break 'outer;
                    }
                }
                if sum > target {
                    r -= 1;
                } else {
                    l += 1;
                }
            }
        }
        res.expect("no")
    }
}
// @lc code=end