CODE 115. 3Sum Closest

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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).

public int threeSumClosest(int[] num, int target) {
	// IMPORTANT: Please reset any member data you declared, as
	// the same Solution instance will be reused for each test case.
	if (num.length <= 2) {
		return -1;
	}
	Arrays.sort(num);
	int targetClosest = Integer.MAX_VALUE;
	for (int i = 0; i < num.length - 2; i++) {
		int sum = num[i];
		int start = i + 1;
		int end = num.length - 1;
		while (start < end) {
			if (targetClosest == Integer.MAX_VALUE
					|| (Math.abs(num[start] + num[end] + sum - target) < Math
							.abs(targetClosest - target))) {
				targetClosest = num[start] + num[end] + sum;
			}
			if (num[start] + num[end] > target - sum) {
				while (start < end && num[end - 1] == num[end]) {
					end--;
				}
				end--;
			} else if (num[start] + num[end] < target - sum) {
				while (start < end && num[start + 1] == num[start]) {
					start++;
				}
				start++;
			} else {
				return target;
			}
		}
		while (i < num.length - 2 && num[i + 1] == num[i]) {
			i++;
		}
	}
	return targetClosest;
}