Question：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).
class Solution {
public:
int threeSumClosest(vector<int>& nums, int target)
{
}
};
本題還是考察夾逼
class Solution {
public:
int threeSumClosest(vector<int>& nums, int target)
{
sort( nums.begin(), nums.end() );
int size = nums.size();
int result=0;
int min_gap=INT32_MAX;
auto last=nums.end();
for (auto i=nums.begin(); i<(last-2); i++)
{
if( i>nums.begin() && *i == *(i-1) ) continue;
auto j=(i+1);
auto k=last-1;
while( j<k )
{
int sum = (*i) + (*j) + (*k);
int gap=abs(sum-target);
if(gap<min_gap)
{
min_gap=gap;
result=sum;
}
if (sum < target) j++;
else k--;
}
}
return result;
}
};
