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).
Solution
The solution is similar to 3 sum. The difference is we need to have a closest variable to mark the current sum that is closest to target.
Code
class Solution {
public int threeSumClosest(int[] nums, int target) {
Arrays.sort(nums);
int closest = nums[0] + nums[1] + nums[2];
for(int i=0; i<nums.length-2; i++) {
int l = i+1;
int r = nums.length-1;
while(l<r) {
int sums = nums[i] + nums[l] + nums[r];
if(Math.abs(target - sums) < Math.abs(target - closest))
closest = sums;
if(closest == target) return closest;
if(target > sums) {
l++;
}
else {
r--;
}
}
}
return closest;
}
}
Performance
Same to 3 sum, the time complexity is O(n). The space complexity is O(1)