LeetCode No16. 最接近的三数之和

class Solution {
    
    public int threeSumClosest(int[] nums, int target) {
        int len = nums.length;
        Arrays.sort(nums);
        int res = 100000;
        // 如何剪枝
        for(int first=0; first<len; first++) {
            for(int second = first+1; second<len; second++) {
                // 这层应该是不需要的，有超时风险
                for(int thread = second+1; thread<len; thread++) {
                    int num = nums[first]+nums[second]+nums[thread];
                    if( Math.abs(target-num)<=Math.abs(target-res) ) {
                        res = num;
                    }
                }
            }
        }
        return res;
    }
}

class Solution {
    
    public int threeSumClosest(int[] nums, int target) {
        int len = nums.length;
        Arrays.sort(nums);
        int res = 100000;
        for(int i=0; i<len-2; i++) {
            if( i!=0 && nums[i]==nums[i-1] ) {
                continue;
            }
            int j = i + 1, k = len - 1;
            while (j < k) {
                int sum = nums[i] + nums[j] + nums[k];
                if (sum == target) {
                    return target;
                }
                if (Math.abs(sum - target) < Math.abs(res - target)) {
                    res = sum;
                }
                if (sum > target) {
                    int k0 = k - 1;
                    while (j < k0 && nums[k0] == nums[k]) {
                        --k0;
                    }
                    k = k0;
                } else {
                    // 如果和小于 target，移动 b 对应的指针
                    int j0 = j + 1;
                    // 移动到下一个不相等的元素
                    while (j0 < k && nums[j0] == nums[j]) {
                        ++j0;
                    }
                    j = j0;
                }
            }
        }
        return res;
    }
}