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
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
#include <bits/stdc++.h>
using namespace std;

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin >> n;
    vector<int> dec(n), inc(n);
    for (auto &i : dec)
        cin >> i;
    inc = dec;
    int res1 = 0, res2 = 0;
    int czyrosnie = 1;
    for (int i = 1; i < n; ++i)
    {
        if (czyrosnie == 0 && dec[i] >= dec[i - 1])
        {
            if (dec[i - 1] == -1e9)
            {
                res1 = INT_MAX;
                break;
            }
            res1++;
            dec[i] = -1e9;
        }
        else if (czyrosnie == 1 && dec[i] <= dec[i - 1])
        {
            if (dec[i - 1] == 1e9)
            {
                res1 = INT_MAX;
                break;
            }
            res1++;
            dec[i] = 1e9;
        }
        czyrosnie ^= 1;
    }
    czyrosnie = 0;
    for (int i = 1; i < n; ++i)
    {
        if (czyrosnie == 0 && inc[i] >= inc[i - 1])
        {
            if (inc[i - 1] == -1e9)
            {
                res2 = INT_MAX;
                break;
            }
            res2++;
            inc[i] = -1e9;
        }
        else if (czyrosnie == 1 && inc[i] <= inc[i - 1])
        {
            if (inc[i - 1] == 1e9)
            {
                res2 = INT_MAX;
                break;
            }
            res2++;
            inc[i] = 1e9;
        }
        czyrosnie ^= 1;
    }
    int ans = min(res1, res2);
    cout << ans << endl;
}