# Why my code is running so slow?

• This is my code tooks 12ms to solve this problem.

``````int threeSumClosest(std::vector<int>& nums, int target)
{
if (nums.size() == 3)
return nums[0] + nums[1] + nums[2];
int ret{ 2147483647 };
sort(nums.begin(), nums.end());
for (int i = 0; i < nums.size() - 2;i++)
{
int l = i + 1, u = nums.size() - 1;
while (l < u)
{
int distance = nums[l] + nums[u] + nums[i] - target;
ret = abs(ret) < abs(distance) ? ret : distance;
if (distance > 0)
u--;
else if (distance < 0)
l++;
else
return target;
}
}
return ret + target;
}
``````

This is another code only tooks 6ms to solve this problem.

``````    int threeSumClosest(vector<int>& nums, int target) {
if (nums.size() == 3)
return nums[0] + nums[1] + nums[2];

sort(nums.begin(), nums.end());
int result = 10000;
int result_tmp = 10000;
for (int i = 0; i < nums.size() - 2; i++)
{
int left = i + 1;
int right = nums.size() - 1;
while (left < right)
{
int tmp = nums[i] + nums[left] + nums[right] - target;
result_tmp = (abs(result_tmp) < abs(tmp)) ? result_tmp : tmp;
if (tmp < 0)
left++;
else if (tmp > 0)
right--;
else
return target;
}
}
return result_tmp + target;
}
``````

I think the two codes use the same algorithm and have the same time complexity(O(N*N)). The two codes also have the same logic. Why the first code is so slow?
Note: The first code took 12ms, the second only 6ms.

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