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16. 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).
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/**
* Runtime: 4 ms, faster than 96.20% of Java online submissions for 3Sum Closest.
*
* Memory Usage: 36.1 MB, less than 100.00% of Java online submissions for 3Sum Closest.
*
* @author D瓜哥 · https://www.diguage.com
* @since 2018-07-15 00:55
*/
public int threeSumClosest(int[] nums, int target) {
if (Objects.isNull(nums)) {
return target;
}
Arrays.sort(nums);
int length = nums.length;
int result = 0;
int difference = Integer.MAX_VALUE;
for (int head = 0; head < length; head++) {
int midd = head + 1;
int tail = length - 1;
while (midd < tail) {
int sum = nums[head] + nums[midd] + nums[tail];
if (sum > target) {
while (midd < tail && nums[tail - 1] == nums[tail]) {
tail--;
}
tail--;
} else if (sum < target) {
while (midd < tail && nums[midd] == nums[midd + 1]) {
midd++;
}
midd++;
} else {
return target;
}
int tempDiff = Math.abs(sum - target);
if (tempDiff < difference) {
result = sum;
difference = tempDiff;
}
}
}
return result;
}
/**
* Runtime: 73 ms, faster than 7.18% of Java online submissions for 3Sum Closest.
*
* Memory Usage: 36.7 MB, less than 100.00% of Java online submissions for 3Sum Closest.
*/
public int threeSumClosestO3(int[] nums, int target) {
if (Objects.isNull(nums)) {
return target;
}
int length = nums.length;
if (length <= 3) {
int result = 0;
for (int i = 0; i < length; i++) {
result += nums[i];
}
return result;
}
int result = 0;
int difference = Integer.MAX_VALUE;
for (int i = 0; i < length; i++) {
for (int j = i + 1; j < length; j++) {
for (int k = j + 1; k < length; k++) {
int sum = nums[i] + nums[j] + nums[k];
int temp = Math.abs(target - sum);
if (temp < difference) {
difference = temp;
result = sum;
}
}
}
}
return result;
}