16.cpp

// sort.cpp
class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        sort(nums.begin(), nums.end());
        int t = 0x7fffffff, j, k, n = nums.size(), s;
        for (int i = 0; i < n; ++i) {
            s = target - nums[i];
            for (j = i + 1, k = n - 1; j < k;) {
                int sum = nums[j] + nums[k];
                if (abs(t) > abs(sum - s))
                    t = sum - s;
                if (sum > s)
                    k--;
                else if (sum < s)
                    ++j;
                else
                    return target;
            }
        }
        return target + t;
    }
};
class Solution2 {
public:
    int threeSumClosest(vector<int> nums, int target) {
        sort(nums.begin(), nums.end());
        int ret = 1000000;
        auto find = [&ret, &target](vector<int>& nums, int k) {
            int i = k + 1, j = nums.size() - 1;
            while (i < j) {
                int sum = nums[i] + nums[j] + nums[k];
                if (abs(sum - target) < abs(ret - target)) {
                    ret = sum;
                }
                if (sum > target) {
                    --j;
                } else if (sum < target) {
                    ++i;
                } else {
                    return;
                }
            }
        };
        for (int k = 0; k < nums.size(); ++k) {
            find(nums, k);
            if (ret == target)
                return ret;
        }
        return ret;
    }
};