Description
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).
Solution
Three-pointers, O(n^2) time
class Solution {
public int threeSumClosest(int[] nums, int target) {
int res = nums[0] + nums[1] + nums[2]; // important, don't set to MAX_VALUE
Arrays.sort(nums);
int i = 0;
int n = nums.length;
while (i < n) {
int j = i + 1;
int k = n - 1;
while (j < k) {
int sum = nums[i] + nums[j] + nums[k];
if (sum < target) {
++j;
} else if (sum > target) {
--k;
} else {
return sum;
}
if (Math.abs(sum - target) < Math.abs(res - target)) {
res = sum;
}
}
++i;
}
return res;
}
}
