LeetCode 16.3Sum Closest

思路：

1. 初始状态
   
   2.三数之和小于target
   
   3.三数之和大于target
   
   4.second和third相遇后first++
   
   5.末尾状态
   

class Solution {
public:
	int threeSumClosest(vector<int>& nums, int target) {
		int minVal = 2147483647;
		int m = 0, n = 0, r = 0;
		sort(nums.begin(), nums.end());
		for (int i = 0; i < nums.size(); ++i) {
			for (int j = i + 1, k = nums.size() - 1; j < k; ) {
				if (nums[i] + nums[j] + nums[k] == target) {
					return target;
				}
				else if(nums[i] + nums[j] + nums[k] > target) {
					if (minVal > abs(nums[i] + nums[j] + nums[k] - target)) {
						minVal = abs(nums[i] + nums[j] + nums[k] - target);
						m = i;
						n = j;
						r = k;
						
					}
                    --k;
				}
				else {
					if (minVal > abs(nums[i] + nums[j] + nums[k] - target)) {
						minVal = abs(nums[i] + nums[j] + nums[k] - target);
						m = i;
						n = j;
						r = k;
					}
                    ++j;
				}
			}
		}
		return nums[m] + nums[n] + nums[r];
	}
};