594. Longest Harmonious Subsequence 最长的和谐子序列

public class Solution {
    public int FindLHS(int[] nums) {
		if (nums.Length == 0) {
			return 0;
		}
		Array.Sort(nums);
		Dictionary<int, int> dict = new Dictionary<int, int>();
		for(int i = 0; i < nums.Length; i++) {
			int num = nums[i];
			int val = 0;
			dict.TryGetValue(num, out val);
			if (val > 0) {
				dict[num]++;
			} else {
				dict[num] = 1;
			}
		}
		int sum = 0;
		int? lastKey = null;
		foreach(int i in dict.Keys) {
			if (lastKey == null) {
				lastKey = i;
				continue;
			}
			int lk = (int)lastKey;
			if (Math.Abs(i - lk) == 1) {
				sum = Math.Max(sum, dict[i] + dict[lk]);
			}
			lastKey = i;
		}
		return sum;
    }
}