题目传送门
1 /*
2 DP：先用l，r数组记录前缀后缀上升长度，最大值会在三种情况中产生：
3 1. a[i-1] + 1 < a[i+1]，可以改a[i]，那么值为l[i-1] + r[i+1] + 1
4 2. l[i-1] + 1 3. r[i+1] + 1 //修改a[i]
5 */
6 #include <cstdio>
7 #include <algorithm>
8 #include <cstring>
9 using namespace std;
10
11 const int MAXN = 1e5 + 10;
12 const int INF = 0x3f3f3f3f;
13 int a[MAXN];
14 int l[MAXN], r[MAXN];
15 int n;
16
17 int main(void) //Codeforces Round #FF (Div. 1) A. DZY Loves Sequences
18 {
19 scanf ("%d", &n); int ans = 0;
20 for (int i=1; i<=n; ++i)
21 {
22 scanf ("%d", &a[i]);
23 l[i] = 1;
24 if (i > 1 && a[i] > a[i-1]) l[i] = l[i-1] + 1;
25 }
26
27 for (int i=n; i>=1; --i)
28 {
29 r[i] = 1;
30 if (i < n && a[i] < a[i+1]) r[i] = r[i+1] + 1;
31 }
32
33 for (int i=1; i<=n; ++i)
34 {
35 ans = max (ans, l[i]); ans = max (ans, r[i]);
36 if (i > 1 && i < n && a[i-1] + 1 < a[i+1]) ans = max (ans, l[i-1] + r[i+1] + 1);
37 if (i > 1) ans = max (ans, l[i-1] + 1);
38 if (i < n) ans = max (ans, r[i+1] + 1);
39 }
40
41 printf ("%d
", ans);
42
43 return 0;
44 }