594. Longest Harmonious Subsequence

QUESTION:

We define a harmonious array is an array where the difference between its maximum value and its minimum value is exactly 1.

Now, given an integer array, you need to find the length of its longest harmonious subsequence among all its possible subsequences.

Example 1:

Input: [1,3,2,2,5,2,3,7]
Output: 5
Explanation: The longest harmonious subsequence is [3,2,2,2,3].

Note: The length of the input array will not exceed 20,000.

EXPLANATION:

这是我第一次提交打败了100%的人，真的有点开心哈。

其实一开始的思路是放在hashtable中，但是没想到提交后发现 -1，1，2的hash顺序竟然是2，-1，1.这就很尴尬了，没有办法，只能想其他的办法。

于是找到了下面的思路：

1.获取当前key的个数count

2.与前一个对比（先判断是不是1）

3.将自己作为前一个

SOLUTION:

public class Solution {
    public int findLHSHelper(int[] nums,int key,int index){
        int count = 0;
        for(int i = index;i<nums.length;i++){
            if(nums[i]==key)
                count++;
            if(nums[i]!=key)
                break;
        }
        return count;
    }
    public int findLHS(int[] nums) {
        if (nums == null || nums.length < 2) return 0;
        Arrays.sort(nums);
        int index = 0;
        int pre = nums[0];
        Integer preCount = null;
        int result = 0;
        while (index < nums.length) {
            int key = nums[index];
            int count = findLHSHelper(nums, key, index);
            index += count;

            if (preCount == null || Math.abs(pre - key) > 1) {
                preCount = count;
                pre = key;
                continue;
            }

            result = Math.max(result, preCount + count);
            preCount = count;
            pre = key;
        }
        return result;
    }
}
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