给定一个整型数组和一个target，求数组中两个数的和为target并返回其下标索引

package company.airbnb;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
public class AddTwoSum {
    public static void main(String args[]) {
        int[] arr = {2, 134, 15, 5, 7, 264, 423, 45, 3, 36};
        System.out.println(twoSum3(arr, 18)[0] + "," + twoSum3(arr, 18)[1]);
    }
    // 最简单的方法，循环判断，通过了
    public static int[] twoSum1(int[] nums, int target) {
        int a = 0;
        int b = 0;
        for (int i = 0; i < nums.length - 1; i++)
            for (int j = i + 1; j < nums.length; j++) {
                if ((nums[i] + nums[j]) == target) {
                    a = i;
                    b = j;
                    break;
                }
            }
        return new int[]{a, b};
    }
    // 采用hash表存储键值对(number[i],i),然后判断target-numbers[i]是否在hash表中
    public static int[] twoSum2(int[] numbers, int target) {
        int[] res = new int[2];
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        for (int i = 0; i < numbers.length; i++) {
            if (map.containsKey(target - numbers[i])) {
                res[0] = map.get(target - numbers[i]);
                res[1] = i;
                return res;
            } else {
                map.put(numbers[i], i);
            }
        }
        return res;
    }
    // 双指针实现
    public static int[] twoSum3(int[] arr, int sum) {
        if (arr == null) {
            return null;
        }
        int low = 0;
        int high = arr.length - 1;
        int[] result = {-1, -1};
        // 先排序
        Arrays.sort(arr, low, high);
        while (low < high) {
            if (arr[low] + arr[high] == sum) {
                if (arr[low] > arr[high]) {
                    result[0] = high;
                    result[1] = low;
                } else {
                    result[0] = low;
                    result[1] = high;
                }
                break;
            } else if (arr[low] + arr[high] > sum) {
                high--;
            } else {
                low++;
            }
        }
        return result;
    }
}