Leetcode 217. Contains Duplicate

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

思路：
用哈希表记录已遍历的数字。

public boolean containsDuplicate(int[] nums) {
    if (nums == null || nums.length <= 1) {
        return false;
    }

    HashSet<Integer> set = new HashSet<>();
    for (int num : nums) {
        if (!set.add(num)) {
            return true;
        }
    }

    return false;
}

先对数组排序，然后看有没有相等的相邻数字。

public boolean containsDuplicate(int[] nums) {

    Arrays.sort(nums);
    for(int ind = 1; ind < nums.length; ind++) {
        if(nums[ind] == nums[ind - 1]) {
            return true;
        }
    }
    return false;
}