两指针（6）

原题：

/** * Created by gouthamvidyapradhan on 13/06/2017. * Accepted * 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. * <p> * For example, given array S = {-1 2 1 -4}, and target = 1. * <p> * The sum that is closest to the target is 2. (-1 + 2 + 1 = 2). */

答案：

public class ThreeSumClosest {    public static void main(String[] args) {        int[] a = {-1, 2, 1, -4};        System.out.println(new ThreeSumClosest().threeSumClosest(a, 1));    }    public int threeSumClosest(int[] a, int target) {        Arrays.sort(a);        int min = Integer.MAX_VALUE, ans = -1;        for (int i = 0, l = a.length; i < l - 2; i++) {            if (i == 0 || !(a[i] == a[i - 1])) {                int j = i + 1, k = l - 1;                while (k > j) {                    if (j != i + 1 && (a[j] == a[j - 1])) {                        j++;                        continue;                    }                    int sum = a[i] + a[j] + a[k];                    if (sum < target) {                        int diff = Math.abs(sum - target);                        if (diff < min) {                            min = diff;                            ans = sum;                        }                        j++;                    } else if (sum > target) {                        int diff = Math.abs(sum - target);                        if (diff < min) {                            min = diff;                            ans = sum;                        }                        k--;                    } else {                        return sum;                    }                }            }        }        return ans;    }}