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Program.cs
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Program.cs
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//如果数组长度小于2,直接返回数组长度。
//利用状态机编程思想,设立begin,up,down三个状态。将初始状态设为begin。begin状态可以切换成up或down两种状态,up和down只能相互切换。
//从第二个元素开始遍历数组利用switch语句在三种状态间切换。让每个元素与之前一元素比较决定是否切换状态,每当状态切换时maxLen加一。
using System;
namespace WiggleSubsequence
{
class Program
{
static void Main(string[] args)
{
int[] nums = { 1, 7, 4, 9, 2, 5 };
Console.WriteLine(WiggleMaxLength(nums));
}
static int WiggleMaxLength(int[] nums)
{
if (nums.Length < 2)
return nums.Length;
const string begin = "begin";
const string up = "up";
const string down = "down";
string state = begin;
int maxLen = 1;
for (int i = 1; i < nums.Length; i++)
{
switch (state) //Line 26 - 54 是使用状态机检查状态是否发生变化。
{
case begin:
if (nums[i] > nums[i - 1])
{
state = up;
maxLen++;
}
else if(nums[i] < nums[i - 1])
{
state = down;
maxLen++;
}
break;
case up:
if (nums[i] < nums[i - 1])
{
state = down;
maxLen++;
}
break;
case down:
if (nums[i] > nums[i - 1])
{
state = up;
maxLen++;
}
break;
}
}
return maxLen;
}
}
}