1346. Intervals of Monotonicity（ｄｐ）

１３４６

简单ｄｐ

 1 #include <iostream>

 2 #include<cstdio>

 3 #include<cstring>

 4 #include<algorithm>

 5 #include<stdlib.h>

 6 #include<vector>

 7 using namespace std;

 8 #define N 200010

 9 int p[N],dp[N][2];

10 int main()

11 {

12     int i,a,b;

13     scanf("%d%d",&a,&b);

14     for(i = 1 ; i <= b-a+1 ; i++)

15     scanf("%d",&p[i]);

16     dp[1][0] = 1;

17     dp[1][1] = 1;

18     for(i = 2; i <= b-a+1 ; i++)

19     {

20         if(p[i]>p[i-1])

21         {

22             dp[i][0] = min(dp[i-1][1]+1,dp[i-1][0]);

23             dp[i][1] = min(dp[i-1][0]+1,dp[i-1][1]+1);

24         }

25         else if(p[i]<p[i-1])

26         {

27             dp[i][0] = min(dp[i-1][1]+1,dp[i-1][0]+1);

28             dp[i][1] = min(dp[i-1][0]+1,dp[i-1][1]);

29         }

30         else

31         {

32             dp[i][0] = min(dp[i-1][0],dp[i-1][1]+1);

33             dp[i][1] = min(dp[i-1][1],dp[i-1][0]+1);

34         }

35     }

36     int ans = min(dp[b-a+1][0],dp[b-a+1][1]);

37     printf("%d\n",ans);

38     return 0;

39 }

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