16. 3Sum Closest (Medium)
https://leetcode.com/problems/3sum-closest/
Given an array nums
of n integers and an integer target
, find three integers in nums
such that the sum is closest to target
. Return the sum of the three integers. You may assume that each input would have exactly one solution.
Example:
Given array nums = [-1, 2, 1, -4], and target = 1. The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
Solutions
class Solution {
// Solution for Problem 15 is a good template. Memorize it as possible as you can.
public int threeSumClosest(int[] nums, int target) {
Arrays.sort(nums);
int ans = -1;
int min = Integer.MAX_VALUE;
for (int i = 0, l = nums.length; i < l - 2; i++) {
// nums[i - 1] is already calculated, skip nums[i] if same value with previous one
if (i != 0 && nums[i] == nums[i - 1]) {
continue;
}
int j = i + 1;
int k = l - 1;
while (j < k) {
// skip already compared element
if (j != i + 1 && (nums[j] == nums[j - 1])) {
j++;
continue;
}
// Since one exact solution only, stop searching to once found
int sum = nums[i] + nums[j] + nums[k];
if (sum == target) {
return sum;
}
// distance to target value, positive value
int dist = Math.abs(sum - target);
if (dist < min) {
min = dist;
ans = sum;
}
if (sum < target) {
j++; // approach target with larger value
}
if (sum > target) {
k--; // approach target with smaller value
}
}
}
return ans;
}
}