D. Dog Show 2017-2018 ACM-ICPC, NEERC, Southern Subregional Contest, qualification stage (Online Mirror, ACM-ICPC Rules, Teams Preferred)

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <time.h>
 6 #include <string>
 7 #include <set>
 8 #include <map>
 9 #include <list>
10 #include <stack>
11 #include <queue>
12 #include <vector>
13 #include <bitset>
14 #include <ext/rope>
15 #include <algorithm>
16 #include <iostream>
17 using namespace std;
18 #define ll long long
19 #define minv 1e-6
20 #define inf 1e9
21 #define pi 3.1415926536
22 #define E  2.7182818284
23 const ll mod=1e9+7;//998244353
24 const int maxn=2e5+10;
25 
26 vector<int>b;
27 vector<int>::iterator j;
28 int a[maxn];
29 
30 priority_queue<int>s;
31 
32 int main()
33 {
34     int n,m,i,a,sum=0,g=0;
35     scanf("%d%d",&n,&m);
36     for (i=1;i<=min(m-1,n);i++)
37     {
38         scanf("%d",&a);
39         if (a>=m)
40             continue;
41         while (!s.empty() && s.top()>=m-i)
42         {
43             s.pop();
44             g--;
45         }
46         s.push(a-i);
47         g++;
48         sum=max(sum,g);
49     }
50     cout<<sum;
51     return 0;
52 }