Merge pull request 6boris#48 from kylesliu/develop

add 376 problem solution

Author: 6boris

assets/images/376_Wiggle_Subsequence.jpg

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+# [376. Wiggle Subsequence][title]
+
+## Description
+
+A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The first difference (if one exists) may be either positive or negative. A sequence with fewer than two elements is trivially a wiggle sequence.
+
+For example, [1,7,4,9,2,5] is a wiggle sequence because the differences (6,-3,5,-7,3) are alternately positive and negative. In contrast, [1,4,7,2,5] and [1,7,4,5,5] are not wiggle sequences, the first because its first two differences are positive and the second because its last difference is zero.
+
+Given a sequence of integers, return the length of the longest subsequence that is a wiggle sequence. A subsequence is obtained by deleting some number of elements (eventually, also zero) from the original sequence, leaving the remaining elements in their original order.
+
+**Example 1:**
+
+```
+Input: [1,7,4,9,2,5]
+Output: 6
+Explanation: The entire sequence is a wiggle sequence.
+```
+
+**Example 2:**
+
+```
+Input: [1,17,5,10,13,15,10,5,16,8]
+Output: 7
+Explanation: There are several subsequences that achieve this length. One is [1,17,10,13,10,16,8].
+```
+
+**Example 3:**
+
+```
+Input: [1,2,3,4,5,6,7,8,9]
+Output: 2
+```
+
+**Tags:** Math, String
+
+## 题意
+>求摇摆序列最长序列，可以转化为数组【上升】【下降】状态的转换
+
+<a href="https://github.com/kylesliu/awesome-golang-leetcode/tree/master/assets/images/376_Wiggle_Subsequence.jpg">
+    <img src="https://github.com/kylesliu/awesome-golang-leetcode/tree/master/assets/images/376_Wiggle_Subsequence.jpg" />
+</a>
+
+## 题解
+
+### 思路1
+> 按照小学算数那么来做，用 `carry` 表示进位，从后往前算，依次往前，每算出一位就插入到最前面即可，直到把两个二进制串都遍历完即可。
+
+```go
+func wiggleMaxLength(nums []int) int {
+	//	序列个数小于二直接是摇摆序列
+	if len(nums) < 2 {
+		return len(nums)
+	}
+	//	3种状态
+	const BEGIN, UP, DOWN = 0, 1, 2
+	//	摇摆序列最小长度至少为1
+	STATE, maxLength := BEGIN, 1
+
+	for i := 1; i < len(nums); i++ {
+		switch STATE {
+		case BEGIN:
+			if nums[i-1] < nums[i] {
+				STATE = UP
+				maxLength++
+			} else if nums[i-1] > nums[i] {
+				STATE = DOWN
+				maxLength++
+			}
+		case UP:
+			if nums[i-1] > nums[i] {
+				STATE = DOWN
+				maxLength++
+			}
+		case DOWN:
+			if nums[i-1] < nums[i] {
+				STATE = UP
+				maxLength++
+			}
+		}
+	}
+	return maxLength
+}
+
+```
+
+### 思路2
+> 思路2
+```go
+
+```
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-leetcode][me]
+
+[title]: https://leetcode.com/problems/wiggle-subsequence/
+[me]: https://github.com/kylesliu/awesome-golang-leetcode

src/0376.Wiggle-Subsequence/README.md

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+package Solution
+
+func wiggleMaxLength(nums []int) int {
+	//	序列个数小于二直接是摇摆序列
+	if len(nums) < 2 {
+		return len(nums)
+	}
+	//	3种状态
+	const BEGIN, UP, DOWN = 0, 1, 2
+	//	摇摆序列最小长度至少为1
+	STATE, maxLength := BEGIN, 1
+
+	for i := 1; i < len(nums); i++ {
+		switch STATE {
+		case BEGIN:
+			if nums[i-1] < nums[i] {
+				STATE = UP
+				maxLength++
+			} else if nums[i-1] > nums[i] {
+				STATE = DOWN
+				maxLength++
+			}
+		case UP:
+			if nums[i-1] > nums[i] {
+				STATE = DOWN
+				maxLength++
+			}
+		case DOWN:
+			if nums[i-1] < nums[i] {
+				STATE = UP
+				maxLength++
+			}
+		}
+	}
+	return maxLength
+}

src/0376.Wiggle-Subsequence/Solution.go

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+package Solution
+
+import (
+	"reflect"
+	"strconv"
+	"testing"
+)
+
+func TestSolution(t *testing.T) {
+	//	测试用例
+	cases := []struct {
+		name   string
+		inputs []int
+		expect int
+	}{
+		{"TestCase", []int{1, 7, 4, 9, 2, 5}, 6},
+		{"TestCase", []int{1, 17, 5, 10, 13, 15, 10, 5, 16, 8}, 7},
+		{"TestCase", []int{1, 2, 3, 4, 5, 6, 7, 8, 9}, 2},
+	}
+
+	//	开始测试
+	for i, c := range cases {
+		t.Run(c.name+strconv.Itoa(i), func(t *testing.T) {
+			got := wiggleMaxLength(c.inputs)
+			if !reflect.DeepEqual(got, c.expect) {
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
+					c.expect, got, c.inputs)
+			}
+		})
+	}
+}
+
+//	压力测试
+func BenchmarkSolution(b *testing.B) {
+
+}
+
+//	使用案列
+func ExampleSolution() {
+
+}