codeforces Round#695 div2 B题

#include <bits/stdc++.h>
using namespace std;
 
const int N = 3e5;
int n, a[N];
 
bool check(int i) {
    
    
	if (i <= 0 || i >= n - 1) return false;
	return (a[i - 1] < a[i] && a[i] > a[i + 1]) || (a[i - 1] > a[i] && a[i] < a[i + 1]);
}
 
int count(int i) {
    
    
	return check(i - 2) + check(i - 1) + check(i) + check(i + 1) + check(i + 2);
}
 
int main() {
    
    
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int tt;
    cin >> tt;
    while (tt--) {
    
    
    	cin >> n;
    	for (int i = 0; i < n; ++i) {
    
    
    		cin >> a[i];
    	}
    	int d = 0, cnt =  0;
    	for (int i = 1; i < n - 1; ++i) {
    
    
    		if (check(i)) {
    
    
    			++cnt;
    		}
    	}
    	for (int i = 1; i < n - 1; ++i) {
    
    
    		if (check(i)) {
    
    
    			int tmp = a[i];
    			int prev = count(i);
    			a[i] = a[i - 1];
    			int curr = count(i);
    			d = max(d, prev - curr);
    			a[i] = a[i + 1];
    			curr = count(i);
    			d = max(d, prev - curr);
    			a[i] = tmp;
    		}
    	}
    	cout << max(0, cnt - d) << '\n';
    }
    return 0;
}

妈妈呀，读错题了。。。