[LeetCode16]3Sum Closest

题目：

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.

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).

分类：Array TwoPointers

代码：

class Solution {
public:
int threeSumClosest(vector<int>& nums, int target)
{
int n = nums.size();
int sum = 0;
if(n <= 3)
{
return accumulate(nums.begin(),nums.end(),0);
}
sort(nums.begin(),nums.end());

int temp = nums[0] + nums[1] + nums[2];
for(int i = 0; i < n - 2; ++i)
{
int j = i + 1;
int k = n - 1;
while(j < k)
{
sum = nums[i] + nums[j] + nums[k];
if(abs(target - sum) < abs(target - temp))
{
temp = sum;
if(temp == target)
return  temp;
}
if(sum > target)
{
k--;
}
else
{
j++;
}
}
}
return  temp;
}
};