LeetCode-16. 3Sum Closest

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).

题解：

class Solution {
public:
  int threeSumClosest(vector<int>& nums, int target) {
    int n = nums.size();
    int ans = nums[0] + nums[1] + nums[2];
    sort(nums.begin(), nums.end());
    for (int i = 0; i < n - 2; i++) {
      int j = i + 1, k = n - 1;
      while (j < k) {
        int sum = nums[i] + nums[j] + nums[k];
        if (sum == target) {
          return sum;
        }
        else if (sum > target) {
          if (sum - target < abs(ans - target)) {
            ans = sum;
          }
          k--;
        }
        else {
          if (target - sum < abs(ans - target)) {
            ans = sum;
          }
          j++;
        }
      }
      while (nums[i] == nums[i + 1]) {
        i++;
      }
    }
    return ans;
  }
};