1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
#include<cstdio>
#include<algorithm>
#define S 50007

using namespace std;

int T[S];
int T2[S];

int main(void){
    int n;
    scanf("%d",&n);
    for(int i = 1; i <= n;i++){
        scanf("%d",&T[i]);
    }
    T2[1] = T[1];
    int p = 0;
    int p2 = 0;
    for(int i = 2; i <= n;i++){
        T2[i] = T[i];
        if(i%2){
            if(T2[i] <= T2[i-1]){
                p++;
                T2[i] = 1000000000;
            }
        }else{
            if(T2[i] >= T2[i-1]){
                p++;
                T2[i] = -1000000000;
            }
        }
    }

    for(int i = 2; i <= n;i++){
        T2[i] = T[i];
        if(i%2){
            if(T2[i] >= T2[i-1]){
                p2++;
                T2[i] = -1000000000;
            }
        }else{
            if(T2[i] <= T2[i-1]){
                p2++;
                T2[i] = 1000000000;
            }
        }
    }
    printf("%d",min(p,p2));
    return 0;
}