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).

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做起来跟3Sum差不多的

public class Solution {
public int threeSumClosest(int[] num, int target) {
Arrays.sort(num);
int ret = num[0] + num[1] + num[2];
int len = num.length;
for (int i = 0; i <= len - 3; i++) {
// first number : num[i]
int j = i + 1;	// second number
int k = len - 1;	// third number
while (j < k) {
int sum = num[i] + num[j] + num[k];
if (Math.abs(sum - target) < Math.abs(ret - target))
ret = sum;
if (sum < target) {
++j;
} else if (sum > target) {
--k;
} else {
++j;
--k;
}
}
}
return ret;
}
}