Codeforces Round #345 (Div. 1) D - Zip-line 带单点修改的LIS 主席树 | 离线树状数组

D - Zip-line

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PII pair<int, int>

using namespace std;

const int N = 4e5 + ;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + ;

int n, m, tot, h[N], hs[N], dp[][N], stk[N], cnt[N], LIS;
bool is[N];

struct ChairmanTree {
    struct node {
        int mx, l, r;
    } a[N * ];
    int tot, root[N];
    void update(int p, int val, int l, int r, int &x, int y) {
        x = ++tot; a[x] = a[y];
        a[x].mx = max(a[x].mx, val);
        if(l == r) return ;
        int mid = l + r >> ;
        if(p <= mid) update(p, val, l, mid, a[x].l, a[y].l);
        else update(p, val, mid + , r, a[x].r, a[y].r);
    }
    int query(int L, int R, int l, int r, int x) {
        if(hs[r] < L || hs[l] > R) return ;
        if(hs[l] >= L && hs[r] <= R) return a[x].mx;
        int ans = , mid = l + r >> ;
        if(L <= hs[mid]) ans = query(L, R, l, mid, a[x].l);
        if(R > hs[mid]) ans = max(ans, query(L, R, mid + , r, a[x].r));
        return ans;
    }
}ct[];

void getLIS() {
    memset(stk, inf, sizeof(stk));
    for(int i = ; i <= n; i++) {
        dp[][i] = lower_bound(stk, stk + N, h[i]) - stk + ;
        stk[dp[][i] - ] = h[i];
        LIS = max(LIS, dp[][i]);
    }
    memset(stk, inf, sizeof(stk));
    for(int i = n; i >= ; i--) {
        dp[][i] = lower_bound(stk, stk + N, -h[i]) - stk + ;
        stk[dp[][i] - ] = -h[i];
    }
    for(int i = ; i <= n; i++) {
        if(dp[][i] + dp[][i] == LIS + ) {
            is[i] = true;
            cnt[dp[][i]]++;
        }
    }
}

int main() {
    scanf("%d%d", &n, &m);
    for(int i = ; i <= n; i++) {
        scanf("%d", &h[i]);
        hs[++tot] = h[i];
    }
    sort(hs + , hs +  + tot);
    tot = unique(hs + , hs +  + tot) - hs - ;

    for(int i = ; i <= n; i++)
        h[i] = lower_bound(hs + , hs +  + tot, h[i]) - hs;
    getLIS();

    for(int i = ; i <= n; i++)
        ct[].update(h[i], dp[][i], , tot, ct[].root[i], ct[].root[i-]);
    for(int i = n; i >= ; i--)
        ct[].update(h[i], dp[][i], , tot, ct[].root[i], ct[].root[i+]);

    while(m--) {
        int a, b;
        scanf("%d%d", &a, &b);
        int ans = is[a] ? LIS -  : LIS;
        ans = max(ans, ct[].query(, b - , , tot, ct[].root[a-])
                  + ct[].query(b + , inf, , tot, ct[].root[a+]) + );
        if(is[a] && cnt[dp[][a]] > ) {
            ans = max(ans, LIS);
        }
        printf("%d\n", ans);
    }
    return ;
}

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