Almost Sorted Array

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <string>
 5 #include <cmath>
 6 using namespace std;
 7 typedef long long ll;
 8 # define INF 0x3f3f3f3f
 9 
10 int main()
11 {
12     ios::sync_with_stdio(false);
13     ll a[100010];
14     ll t, n, f1, f2, pos1, pos2, p1, p2;
15     cin>>t;
16     while( t-- )
17     {
18         cin>>n;
19         f1=0;
20         f2=0;
21         p1=0;
22         p2=0;
23         for(int i=1; i<=n; i++ )
24             cin>>a[i];
25 
26         for(int i=2; i<=n; i++ )
27         {
28             if( a[i]>a[i-1] )
29             {
30                 f1++;
31                 pos1=i;
32             }
33             if( a[i]<a[i-1] )
34             {
35                 f2++;
36                 pos2=i;
37             }
38         }
39 
40         if( f1>1 && f2>1 )
41             cout<<"NO"<<endl;
42         else if( f1==0 || f2==0 )
43             cout<<"YES"<<endl;
44         else
45         {
46             if( f2==1 )
47             {
48                 a[0]=0;
49                 a[n+1] = INF;
50                 if( a[pos2-2]<=a[pos2] || a[pos2-1]<=a[pos2+1] )
51                     p2=1;
52             }
53             if( f1==1 )
54             {
55                 a[n+1]=0;
56                 a[0]=INF;
57                 if( a[pos1-1]>=a[pos1+1] || a[pos1]<=a[pos1-2] )
58                     p1=1;
59             }
60             if( p1||p2 )
61                 cout<<"YES"<<endl;
62             else
63                 cout<<"NO"<<endl;
64         }
65     }
66     return 0;
67 }

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <string>
 5 #include <algorithm>
 6 using namespace std;
 7 
 8 typedef long long ll;
 9 const ll maxn=100005;
10 
11 int n;
12 int LDNS(int a[])
13 {
14     int Cnt=0;
15     int Array[n+1];
16     Array[0]=a[0];
17     for(int i=1; i<n; i++ )
18     {
19         if( a[i]>=Array[Cnt] )
20             Array[++Cnt] = a[i];
21             else
22             {
23                 int Index = upper_bound(Array, Array+Cnt+1, a[i])-Array;
24                 Array[Index] = a[i];
25             }
26     }
27     return Cnt+1;
28 }
29 
30 int main()
31 {
32     int T;
33     int a[maxn], b[maxn];
34     cin>>T;
35     while( T-- )
36     {
37         cin>>n;
38         for(int i=0; i<n; i++ )
39         {
40             cin>>a[i];
41             b[n-i-1]=a[i];
42         }
43         int Len1=LDNS(a);
44         int Len2=LDNS(b);
45         if( Len1>=n-1 || Len2>=n-1 )//若是len1>=n-1,则是最长非递减序列，若是len2>=n-1,则是最长非上升序列
46             cout<<"YES"<<endl;
47             else
48                 cout<<"NO"<<endl;
49     }
50     return 0;
51 }