单调队列

n的算法

通过1.弹出队首 2.压入队尾 3.弹出队尾 来保证区间内的单调性

P1886 滑动窗口 /【模板】单调队列 - 洛谷 | 计算机科学教育新生态 (luogu.com.cn)

#include<bits/stdc++.h>
using namespace std;
const int N=1e6+10;
struct node
{
    int num,poi;
}q[N];
struct nod
{
    int num,poi;
}p[N];
int n,k;
int a[N];
int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;++i)
    cin>>a[i];
    int head=1,tail=1;
    q[head].num=a[1];
    q[tail].poi=1;
    for(int i=1;i<=n;++i)
    {
        //cout<<q[head].num<<endl;
        while(head<=tail&&a[i]<q[tail].num)
        tail--;
        tail++;
        q[tail]=(node){a[i],i};
        while(head<=tail&&q[tail].poi-q[head].poi+1>k)
        head++;
        if(i>=k)
        cout<<q[head].num<<" ";
    }
    cout<<endl;
    head=1;tail=1;
    p[head].num=a[1];
    p[head].poi=1;
    for(int i=1;i<=n;++i)
    {
        while(head<=tail&&a[i]>p[tail].num)
        tail--;
        tail++;
        p[tail]=(nod){a[i],i};
        while(head<=tail&&p[tail].poi-p[head].poi+1>k)
        head++;
        if(i>=k)
        cout<<p[head].num<<" ";
    }
    return 0;
}

P2216 [HAOI2007]理想的正方形 - 洛谷 | 计算机科学教育新生态 (luogu.com.cn)

//双重单调队列
#include<bits/stdc++.h>
using namespace std;
namespace _xzy
{
    typedef long long ll;
    inline int read()
    {
        ll sm=0,flag=1;
        char ch=getchar();
        while(ch<'0'||ch>'9'){if(ch=='-')flag=-1;ch=getchar();}
        while(ch>='0'&&ch<='9'){sm=sm*10+ch-'0';ch=getchar();}
        return sm*flag;
    }
    ll a,b,n,ans=1e9;
    ll g[1002][1002];
    struct node
    {
        ll poi,num;
    }e[1002],d[1002];
    ll maxn[1002][1002],minn[1002][1002];
    void work()
    {
        for(ll i=1;i<=a;++i)
        {
            ll head=1,tail=1,h=1,t=1;
            e[head]=(node){1,g[i][1]};d[head]=(node){1,g[i][1]};
            for(ll j=1;j<=b;++j)
            {
                while(head<=tail&&e[tail].num<g[i][j])tail--;
                tail++;e[tail]=(node){j,g[i][j]};
                while(head<=tail&&e[tail].poi-e[head].poi+1>n)head++;
                
                while(h<=t&&d[t].num>g[i][j])t--;
                t++;d[t]=(node){j,g[i][j]};
                while(h<=t&&d[t].poi-d[h].poi+1>n)h++;
                
                if(j>=n)
                {
                    maxn[i][j]=e[head].num;minn[i][j]=d[h].num;
                }
            }
        }
        for(ll i=n;i<=a;++i)
        for(ll j=n;j<=b;++j)
        {
            ll ma=0,mi=1e9;
            for(ll k=i;k>=i-n+1;--k)
            {
                ma=max(ma,maxn[k][j]);mi=min(mi,minn[k][j]);
            }
            ans=min(ans,abs(ma-mi));
        }
        cout<<ans;
    }
    void My_main()
    {
        a=read();b=read();n=read();
        for(ll i=1;i<=a;++i)
        for(ll j=1;j<=b;++j)
        g[i][j]=read();
        work();
    }
}
int main()
{
    _xzy::My_main();
    return 0;
}