问题 C: 序列交换

 1 #include <bits/stdc++.h>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstdlib>
 5 #include<cstring>
 6 #include<cstdio>
 7 #include<cmath>
 8 //#define DEBUG
 9 using namespace std;
10 typedef long long ll;
11 //typedef __int128 lll;
12 const int N=100000+100;
13 const int MOD=1e9+7;
14 const double PI = acos(-1.0);
15 const double EXP = 1E-8;
16 const int INF = 0x3f3f3f3f;
17 int t,n,m,k,q;
18 int a[N];
19 int b[N];
20 int main()
21 {
22 
23     while(~scanf("%d",&n)){
24         t=0;
25         for(int i=1;i<=n;i++){
26             scanf("%d",&a[i]);
27             b[i]=a[i];
28             if(i!=1&&a[i]<a[i-1]){
29                     t++;
30             }
31         }
32         if(t==1||t==0){
33             if(t==1){
34                 for(int i=2;i<=n;i++){
35                     if(a[i]<a[i-1]){
36                         swap(a[i],a[i-1]);
37                         //break;
38                     }
39                 }
40                 for(int i=2;i<=n;i++){
41                     if(a[i]<a[i-1]){
42                         t=0;
43                         break;
44                     }
45                 }
46                 q=1;
47                 for(int i=n;i>=2;i--){
48                     if(b[i]<b[i-1]){
49                         swap(b[i],b[i-1]);
50                         //break;
51                     }
52                 }
53                 for(int i=2;i<=n;i++){
54                     if(b[i]<b[i-1]){
55                         q=0;
56                         break;
57                     }
58                 }
59                 if(t||q){
60                     cout << "Yes" << endl;
61                 }else{
62                     cout << "No" << endl;
63                 }
64             }else{
65                 cout << "Yes" << endl;
66             }
67         }else{
68             cout << "No" << endl;
69         }
70     }
71 
72     return 0;
73 }