题目

#include<bits/stdc++.h>
using namespace std;
stack <int> s;
int a[1005],n;
int main(){
    cin >> n;
    for(int i=1; i<=n; i++)
        cin >> a[i];
    int t=1;
    for(int i=1; i<=n; i++){
        while(t<=a[i]){
            s.push(t);
            t++;
        }
        if(s.top()==a[i]) s.pop();
        else{
            cout << "NO";
            return 0;
        }
    }
    cout << "YES";
    return 0;
}

#include <bits/stdc++.h>
#define LL long long
using namespace std;
const int N = 1e3 + 10;
const int INF = 0x3f3f3f3f;
int num [N] , last , n , maxc = -INF;
int main()
{
	cin >> n;
	for(int i = 1; i <= n; i++)
		cin >> num[i];
	last = num[1];
	for(int i = 2; i <= n; i++)
	{
		if(num [i] > last)
		{
			if(num[i] < maxc)
			{
				cout << "NO";
				return 0;
			}
		}
		else
		{
			last = num[i];
			maxc = max(maxc,num[i]);
		}
	}
	cout<<"YES";
	return 0;
}

#include<bits/stdc++.h> using namespace std; int n; const int N=1e3+5; stack s; int a[N]; int x=1,kk;

signed main() { cin>>n; for(int i=1;i<=n;i++) { cin>>a[i]; } s.push(1); for(int i=1;i<=n;i++) { s.push(i); kk=n+1; while (kk--){ if(s.top()==a[x]){ s.pop(); x++; } } } if(s.size()==1){ cout<<"YES"; } else{ cout<<"NO"; } return 0; }

#include <bits/stdc++.h> using namespace std; #define N 1005

int main() { int n, a[N], st[N] = {}; cin >> n; for (int i = 1; i <= n; ++i) cin >> a[i]; for (int i = 1; i <= n; ++i) { for (int j = a[i] + 1; j <= n; ++j) { if (st[j] == 1) { cout << "NO"; return 0; } } for (int j = 1; j < a[i]; ++j) { if (st[j] == 0) st[j] = 1; } st[a[i]] = 2; } cout << "YES"; return 0; }

#include <bits/stdc++.h> using namespace std; #define N 1005

int main() { int n, a[N], st[N] = {}; cin >> n; for (int i = 1; i <= n; ++i) cin >> a[i]; for (int i = 1; i <= n; ++i) { for (int j = a[i] + 1; j <= n; ++j) { if (st[j] == 1) { cout << "NO"; return 0; } } for (int j = 1; j < a[i]; ++j) { if (st[j] == 0) st[j] = 1; } st[a[i]] = 2; } cout << "YES"; return 0; }