Leetcode--3Sum Closest

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).

思路：用一个变量res保存当前最接近target的值，如果存在三个数的和值temp满足：abs(temp-target)<abs(res-target)

则更新res（res=temp）

class Solution {
public:
int threeSumClosest(vector<int> &num, int target) {
int res=0x3f3f3f3f;
if(num.size()<3)
return res;
sort(num.begin(),num.end());

for(int i=0;i<num.size()-2;i++)
{
if(i>0&&num[i]==num[i-1]) continue;
int l=i+1;
int r=num.size()-1;
while(l<r)
{
if(l>i+1&&num[l]==num[l-1])
{
l++;
continue;
}

if(r<num.size()-1&&num[r]==num[r+1])
{
r--;
continue;
}

int temp=num[i]+num[l]+num[r];
if(temp==target)
return target;
else if(temp>target)
{
if(abs(temp-target)<abs(res-target))
res=temp;
r--;
}
else if(temp<target)
{
if(abs(temp-target)<abs(res-target))
res=temp;
l++;
}
}
}
return res;
}
};