自我感觉没有问题，不知道问题出在哪，请大佬们帮帮忙，
感激不尽

#include<bits/stdc++.h>
using namespace std;
const int N=50005;

int n;
int a[N],b[N];
int up=INT_MAX;
int down=INT_MIN;
int cnt_up;
int cnt_down;

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);cout.tie(0);
	
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		b[i]=a[i];
	}
		
	//up and down	
	for(int i=1;i<n;i++){
		if(i%2==1&&a[i]<=a[i+1]){
			a[i]=up;
			cnt_up++;
		}
		if(i%2==0&&a[i]>=a[i+1]){
			a[i]=down;
			cnt_up++;
		}
	}
	//down and up
	for(int i=1;i<n;i++){
		if(i%2==1&&b[i]>=b[i+1]){
			b[i]=down;
			cnt_down++;
		}
		if(i%2==0&&b[i]<=b[i+1]){
			b[i]=up;
			cnt_down++;
		}
	}
	
	cout<<min(cnt_up,cnt_down);
	return 0;
}