### 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).

``````import java.util.Arrays;

/**
* Created by gzdaijie on 16/5/15
* 复杂度O(N*lgN + N*N) = O(N)
*/
public class Solution {
public int threeSumClosest(int[] nums, int target) {
Arrays.sort(nums);

int len = nums.length;
int diff = Integer.MAX_VALUE;
int sum, result = 0;
int left, right;

for (int i = 0; i < len - 2; i++) {
// 避免第一个数重复
if (i != 0) {
while (nums[i - 1] == nums[i] && i < len - 2) ++i;
}

left = i + 1;
right = len - 1;
while (left < right) {
sum = nums[i] + nums[left] + nums[right];
if (Math.abs(sum - target) < diff) {
diff = Math.abs(sum - target);
result = sum;
}
if (sum - target > 0) {
--right;
} else if (sum - target < 0) {
++left;
} else {
return target;
}
}
}
return result;
}
}
``````
updated 2016-05-15 01:01:53