LeetCode16 3Sum Closest

题意：

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution. (Medium)

    For example, given array S = {-1 2 1 -4}, and target = 1.

    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

分析：

　　排序、遍历方式顺序 与3 sum思路一致，维护一个与target的差值即可。

代码：

 class Solution {
 public:
     int threeSumClosest(vector<int>& nums, int target) {
         sort(nums.begin(), nums.end());
         int diff = 0x7FFFFFFF;
         for (int i = ; i < nums.size() - ; ++i) {
             int start = i + , end = nums.size() - ;
             while (start < end) {
                 int curSum = nums[i] + nums[start] + nums[end];
                 if (curSum - target == ) {
                     return target;
                 }
                 else if (curSum - target > ) {
                     if (curSum- target < abs(diff) ) {
                         diff = curSum - target;
                     }
                     end--;
                 }
                 else {
                     if (target - curSum < abs(diff)) {
                         diff = curSum - target;
                     }
                     start++;
                 }
             }
         }
         return diff + target;
     }
 };