LeetCode 16 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).

此题与上体3sum类似，只不过这里需要用sum来和target比较决定指针+1,还是-1,同样这里需要先对元素排序，代码如下：

void insertsort2(vector<int> &num)
{
int nSize = num.size();
int j = 0;

for(int i = 1; i< nSize; ++i)
{
int temp = num[i];
for( j = i; j>0 && temp < num[j-1] ; --j)
{
num[j] = num[j-1];
}
num[j] = temp;
}
}
int threeSumClosest(vector<int>& nums, int target)
{
int nSize = nums.size();
int sum = 0;
int dist = INT_MAX;
int nPrevDist = INT_MAX;
insertsort2(nums);

if(nSize < 3)
{
return -1;
}
for(int i = 0; i!=nSize; ++i)
{
int p = i+1;
int q = nSize - 1;
while(p < q)
{
sum = nums[i] + nums
 + nums[q];
int temp = abs(sum - target);
if(temp < nPrevDist)
{
nPrevDist = temp;
dist = sum;
}
if(sum > target)
{
--q;
}
else
{
++p;
}
}
}
return dist;

}