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website/content/ChapterFour/0594.Longest-Harmonious-Subsequence.md

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+# [594. Longest Harmonious Subsequence](https://leetcode.com/problems/longest-harmonious-subsequence/)
+
+
+## 题目
+
+We define a harmounious array as 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](https://en.wikipedia.org/wiki/Subsequence).
+
+**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.
+
+
+## 题目大意
+
+和谐数组是指一个数组里元素的最大值和最小值之间的差别正好是1。现在，给定一个整数数组，你需要在所有可能的子序列中找到最长的和谐子序列的长度。说明: 输入的数组长度最大不超过20,000.
+
+## 解题思路
+
+- 在给出的数组里面找到这样一个子数组：要求子数组中的最大值和最小值相差 1 。这一题是简单题。先统计每个数字出现的频次，然后在 map 找相差 1 的 2 个数组的频次和，动态的维护两个数的频次和就是最后要求的子数组的最大长度。
+
+
+## 代码
+
+```go
+
+package leetcode
+
+func findLHS(nums []int) int {
+	if len(nums) < 2 {
+		return 0
+	}
+	res := make(map[int]int, len(nums))
+	for _, num := range nums {
+		if _, exist := res[num]; exist {
+			res[num]++
+			continue
+		}
+		res[num] = 1
+	}
+	longest := 0
+	for k, c := range res {
+		if n, exist := res[k+1]; exist {
+			if c+n > longest {
+				longest = c + n
+			}
+		}
+	}
+	return longest
+}
+
+```