单调队列

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 using namespace std;
 5 const int N=1000000*2;
 6 int q[N],head,tail,bz[N];
 7 int a[N],n,pos[N],k;
 8 int main()
 9 {
10   scanf("%d%d",&n,&k);
11   for(int i=1;i<=n;++i)
12     scanf("%d",&a[i]);
13     if(k==1)//日常卡数据，请忽略
14     {
15       for(int i=1;i<=n;++i)
16       printf("%d ",a[i]);
17       printf("\n");
18       for(int i=1;i<=n;++i)
19       printf("%d ",a[i]);
20       return 0;
21     }
22   q[++tail]=a[1];pos[tail]=1;
23   for(int i=2;i<k;++i)
24   {
25     while(a[i]<q[tail]&&tail>head) --tail;
26     q[++tail]=a[i];
27     pos[tail]=i;
28   }
29   for(int i=k;i<=n;++i)
30   {
31     bz[i-k]=1;
32     while(bz[pos[head]]==1) head++;
33      while((a[i]<q[tail]||bz[pos[tail]])&&tail>=head)
34     --tail;
35     q[++tail]=a[i];
36     pos[tail]=i;
37     printf("%d ",q[head]);
38   }
39   printf("\n");
40   memset(q,0,sizeof(q));
41   memset(bz,0,sizeof(bz));
42   memset(pos,0,sizeof(pos));
43   tail=1;head=1;
44   q[++tail]=a[1];pos[tail]=1;
45   for(int i=2;i<k;++i)
46   {
47     while(a[i]>q[tail]&&tail>=head) --tail;
48     q[++tail]=a[i];
49     pos[tail]=i;
50   }
51   for(int i=k;i<=n;++i)
52   {
53     bz[i-k]=1;
54     while(bz[pos[head]]==1) head++;
55      while((a[i]>q[tail]||bz[pos[tail]])&&tail>=head)
56     --tail;
57     q[++tail]=a[i];
58     pos[tail]=i;
59     printf("%d ",q[head]);
60   }
61   return 0;
62 }

 1 #include<cstdio>
 2 #include<iostream>
 3 using namespace std;
 4 int n,m;
 5 const int N=500000*2;
 6 int bz[N],pos[N],a[N],q[N],sum[N];
 7 int head=1,tail=0,ans=-0x7fffffff;
 8 int main()
 9 {
10   scanf("%d%d",&n,&m);
11   for(int i=1;i<=n;++i)
12   {
13     scanf("%d",&a[i]);
14     sum[i]=a[i]+sum[i-1];
15   }
16   m++;
17   for(int i=1;i<=n;++i)
18   {
19     if(i>m) bz[i-m]=1;
20     while(bz[pos[head]]) head++;
21     while((sum[i]<q[tail]||bz[pos[tail]])&&tail>=head) tail--;
22     q[++tail]=sum[i];
23     pos[tail]=i;
24     ans=max(ans,sum[i]-q[head]);
25   }
26   printf("%d",ans);
27   return 0;
28 }