sequence

惨遭卡常

#include <bits/stdc++.h>

using namespace std;

typedef pair<int,pair<int,int> > pp;
const int N = 501000;

int read(){
    int x = 0;char ch = getchar();
    while (ch < '0' || '9' < ch) ch = getchar();
    while ('0' <= ch && ch <= '9') x = x * 10 + ch - '0',ch = getchar();
    return x;
}

pp seg[N<<2];
int mx[N<<2];
struct Node{
    int x,y;
    Node(){}
    Node(int x,int y):x(x),y(y){}
}nod[N],sta[N];
struct Node2{
    int x,y,z;
    Node2(){}
    Node2(int x,int y,int z):x(x),y(y),z(z){}
}ques[N];

int n,q,a[N],len,cnt,ans[N];
void init(int,int,int);
void update(int);
void insert(int,int,int,int,int);
int getans(int,int,int,int,int);
pp get(int,int,int,int,int);
pp merge(pp,pp);
bool cmp1(const Node &a,const Node &b){
    return a.x < b.x;
}
bool cmp2(const Node &a,const Node &b){
    return a.y < b.y;
}
bool cmp3(const Node2 &a,const Node2 &b){
    return a.x > b.x;
}
bool cmp4(const Node2 &a,const Node2 &b){
    return a.y < b.y;
}
bool cmp5(const Node &a,const Node &b){
    return a.x > b.x;
}

int main(){
    n = read();q = read();
    for (int i = 1;i <= n;i++) {
        a[i] = read();
        nod[i] = Node(a[i],i);
    }
    for (int i = 1;i <= q;i++){
        int x,y;x = read();y = read();
        ques[i] = Node2(x,y,i);
    }
    sort(nod+1,nod+1+n,cmp1);
    int ncnt = 1;
    for (int i = 2;i <= n;i++)
        if (nod[i].x == nod[i-1].x) nod[i-1].x = ncnt;
        else nod[i-1].x = ncnt++; 
    nod[n].x = ncnt;
    for (int i = 1;i <= n;i++)
        a[nod[i].y] = nod[i].x;
    
    init(1,1,n);
    
    
    len = 1;sta[1] = Node(a[1],1);cnt = 0;
    for (int i = 2;i <= n;i++) {
        while (len && a[i] > sta[len].x){
            int u = sta[len].x,v = sta[len].y;len--;
            while (len && sta[len].x == u){
                nod[++cnt] = Node(sta[len].y,v);
                len--;
            }
        }
        sta[++len] = Node(a[i],i);
    }
    while (len){
        int u = sta[len].x,v = sta[len].y;len--;
        while (len && sta[len].x == u){
            nod[++cnt] = Node(sta[len].y,v); 
            len--;
        }
    }
    
    sort(nod+1,nod+1+cnt,cmp2);
    sort(ques+1,ques+1+q,cmp4);
    int head1 = 1,head2 = 1;
    memset(mx,0,sizeof(mx));
    for (int i = 1;i <= n;i++){
        while (head1 <= cnt && nod[head1].y == i){
            int u = nod[head1].x;
            insert(1,1,n,u,i-u+1);
            head1++;
        }
        while (head2 <= q && ques[head2].y == i){
            int x = ques[head2].x,z = ques[head2].z;
            ans[z] = max(ans[z],getans(1,1,n,x,i));
            head2++;
        }
    }
    
    //part2
    
    len = 1;sta[1] = Node(a[n],n);cnt = 0;
    for (int i = n-1;i >= 1;i--) {
        while (len && a[i] > sta[len].x){
            int u = sta[len].x,v = sta[len].y;len--;
            while (len && sta[len].x == u){
                nod[++cnt] = Node(v,sta[len].y);
                len--;
            }
        }
        sta[++len] = Node(a[i],i);
    }
    while (len){
        int u = sta[len].x,v = sta[len].y;len--;
        while (len && sta[len].x == u){
            nod[++cnt] = Node(v,sta[len].y); 
            len--;
        }
    }
    
    sort(nod+1,nod+1+cnt,cmp5);
    sort(ques+1,ques+1+q,cmp3);
    head1 = 1;head2 = 1;
    memset(mx,0,sizeof(mx));
    for (int i = n;i >= 1;i--){
        while (head1 <= cnt && nod[head1].x == i){
            int u = nod[head1].y;
            insert(1,1,n,u,u-i+1);
            head1++;
        }
        while (head2 <= q && ques[head2].x == i){
            int y = ques[head2].y,z = ques[head2].z;
            ans[z] = max(ans[z],getans(1,1,n,i,y));
            head2++;
        }
    }
    
    
//    part3
    for (int i = 1;i <= q;i++){
        int x = ques[i].x,y = ques[i].y,z = ques[i].z;
        pp g = get(1,1,n,x,y);
        ans[z] = max(ans[z],g.second.second - g.second.first + 1);
        /*
            如果单个点不算答案，这里要特判无解 
            否则恰好包含单个点的情况（原来没考虑到 
        */
    }
    for (int i = 1;i <= q;i++) printf("%d\n",ans[i]);
    return 0;
}
void init(int p,int l,int r){
    if (l == r){
        seg[p].first = a[l];
        seg[p].second = make_pair(l,l);
        return;
    }
    int mid = l + r >> 1;
    init(p<<1,l,mid);
    init(p<<1|1,mid+1,r);
    update(p);
}
void update(int p){
    int u = p<<1,v = u|1;
    if (seg[u].first < seg[v].first) seg[p] = seg[v];
    else if (seg[u].first > seg[v].first) seg[p] = seg[u];
    else{
        seg[p].first = seg[u].first;
        seg[p].second.first = seg[u].second.first;
        seg[p].second.second = seg[v].second.second;
    }
}
void insert(int p,int l,int r,int x,int y){
    mx[p] = max(mx[p],y);
    if (l == r) return;
    int mid = l + r >> 1;
    if (x <= mid) insert(p<<1,l,mid,x,y);
    else insert(p<<1|1,mid+1,r,x,y);
}
int getans(int p,int l,int r,int x,int y){
    if (l == x && r == y) return mx[p];
    int mid = l + r >> 1;
    if (y <= mid) return getans(p<<1,l,mid,x,y);
    else if (mid < x) return getans(p<<1|1,mid+1,r,x,y);
    else return max(getans(p<<1,l,mid,x,mid),getans(p<<1|1,mid+1,r,mid+1,y));
}
pp get(int p,int l,int r,int x,int y){
    if (l == x && r == y) return seg[p];
    int mid = l + r >> 1;
    if (y <= mid) return get(p<<1,l,mid,x,y);
    else if (mid < x) return get(p<<1|1,mid+1,r,x,y);
    else return merge(get(p<<1,l,mid,x,mid),get(p<<1|1,mid+1,r,mid+1,y));
}
pp merge(pp x,pp y){
    pp z;
    if (x.first > y.first) return x;
    else if (x.first < y.first) return y;
    else {
        z.first = x.first;
        z.second.first = x.second.first;
        z.second.second = y.second.second;
        return z;
    }
}