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
#include<bits/stdc++.h>
using namespace std;

const int MAXN = 1e5;

int dp[MAXN][2];

int solve(const vector<int>& t) {
	int n = t.size();

	dp[0][0] = 0;
	dp[0][1] = 1;

	for(int i=1;i<n;i++) {
		int add = ((i%2 == 0 && t[i] < t[i-1]) || (i%2 == 1 && t[i] > t[i-1]) ? 0 : 1);
		dp[i][0] = min(dp[i-1][1], dp[i-1][0] + add);
		dp[i][1] = min(dp[i-1][0], dp[i-1][1]) + 1;
	}

	return min(dp[n-1][0], dp[n-1][1]);
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	int n;
	cin >> n;

	vector<int> t(n);
	for(int& i : t) cin >> i;

	int result = solve(t);
	for(int& i : t) i = -i;
	result = min(result, solve(t));

	cout << result << "\n";

	return 0;
}