E - 只有一端开口的瓶子 Gym - 102174E 【 判断出栈顺序 】

#include <bits/stdc++.h>
#define rep(i,a,b) for(int i = (a); i < (b); i ++)
#define MM(x) memset(x,0,sizeof(x))
#define pb push_back
#define ll long long
using namespace std;
const int maxn = 2e6+5;
int a[maxn];
int main()
{
    int t,n;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d", &n);
        rep(i,0,n)
        {
            scanf("%d", &a[i]);
        }
        stack<int>s;
        while(!s.empty())s.pop();
        int A = 1;
        int ok = 1;
        rep(i,0,n)
        {
            s.push(a[i]);
            while(!s.empty() && s.top() == A)s.pop(),A++;
        }
        if(!s.empty()) ok = 0;
        if(ok)printf("1\n");
        else printf("2\n");
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
# define inf 0x3f3f3f3f
# define ll long long
const int maxn = 2e5+100;
int A[maxn];
int B[maxn];
int st[maxn];
int main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        int n;
        scanf("%d", &n);
        for(int i=0; i<n; i++)
        {
            scanf("%d", &A[i]);
        }
        for(int i = 0; i <n; i ++) B[i] = i+1;
        int j = 0;
        int i = 0;
        int top = 0;
        while(j < n)
        {
            
            if(top != 0 && st[top - 1] == B[j])
            {

                j ++;
                top --;
            }
            else if(A[i] == B[j])
            {
                i ++;
                j ++;

            }
            else if(i < n)
            {
                st[top++] = A[i];
                i ++;
              
            }
            else break;
        }
        
        if(top == 0)printf("1\n");
        else printf("2\n");
    }
return 0;
}
/**
8888
6
6 4 1 2 3 5
5
1 2 3 5 4
*/