Leetcode_0001_TwoSum 两数之和

public class Leetcode_0001_TwoSum {
    public static int[] twoSum(int[] arr, int target) {
        if (arr == null || arr.length <= 0) {
            return new int[2];
        }
        int[] ans = new int[2];
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < arr.length; i++) {
            if (map.containsKey(target - arr[i])) {
                ans[0] = map.get(target - arr[i]);
                ans[1] = i;
                return ans;
            }
            map.put(arr[i], i);
        }
        return ans;
    }
}