题目描述
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).
这道题和3Sum差不多,不过也有不一样的,主要是:
1 这里不用判断处理重复问题
2 要比较其中的三个数的和与目标数的差的大小。
实现代码: class Solution {
public:
int threeSumClosest(vector<int> &num, int target) {
switch (num.size())
{
case 0:
return 0;
case 1:
return num[0];
case 2:
return num[0] + num[1];
default:
break;
}
sort(num.begin(), num.end());
int closet = 0,sum = 0,k=num.size()-1;
int diff = INT_MAX;
for (int i = 0; i < k-1; i++)
{
for (int j = i+1; j < k;)
{
sum = num[i] + num[j] + num[k];
if (sum == target)
{
return sum;
}
if (abs(sum-target) < diff)
{
closet = sum;
diff = abs(sum - target);
}
if (sum < target) j++; //移动左右指针将结果慢慢向target靠;
else k--;
}
}
return closet;
}
};