rt，思路是维护四个线段树

#pragma GCC optimize(3, "Ofast", "inline")
#include <bits/stdc++.h>
#define eb emplace_back
#define int long long
using i64 = long long;
using namespace std;
const int N = 200010;
const int shouge = -1145141919810;
int a[N], b[N], pre1[N], pre2[N];
namespace S1 {
    struct Node {
        int l, r, mx, tag;
        void init(int p) {
            l = r = p;
            mx = pre1[p];
            tag = shouge;
        }
        void push(int v) {
            mx = tag = v;
        }
    } tree[N << 2];
    Node operator+(const Node &l, const Node &r) {
        return {l.l, r.r, max(l.mx, r.mx), shouge};
    }
    void pushdown(int rt) {
        if (shouge != tree[rt].tag) {
            tree[rt << 1].push(tree[rt].tag);
            tree[rt << 1 | 1].push(tree[rt].tag);
            tree[rt].tag = shouge;
        }
    }
    void build(int l, int r, int rt) {
        if (l == r) return tree[rt].init(l);
        int mid = l + r >> 1;
        build(l, mid, rt << 1);
        build(mid + 1, r, rt << 1 | 1);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    void modify(int rt, int ll, int rr, int v) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].push(v);
        int mid = l + r >> 1;
        pushdown(rt);
        if (ll <= mid) modify(rt << 1, ll, rr, v);
        if (mid < rr) modify(rt << 1 | 1, ll, rr, v);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    int query(int rt, int ll, int rr) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].mx;
        int mid = l + r >> 1;
        pushdown(rt);
        int res = -1e18;
        if (ll <= mid) res = max(res, query(rt << 1, ll, rr));
        if (mid < rr) res = max(res, query(rt << 1 | 1, ll, rr));
        return res;
    }
}
namespace S2 {
    struct Node {
        int l, r, mi, tag;
        void init(int p) {
            l = r = p;
            mi = pre2[p];
            tag = shouge;
        }
        void push(int v) {
            mi = tag = v;
        }
    } tree[N << 2];
    Node operator+(const Node &l, const Node &r) {
        return {l.l, r.r, min(l.mi, r.mi), shouge};
    }
    void pushdown(int rt) {
        if (shouge != tree[rt].tag) {
            tree[rt << 1].push(tree[rt].tag);
            tree[rt << 1 | 1].push(tree[rt].tag);
            tree[rt].tag = shouge;
        }
    }
    void build(int l, int r, int rt) {
        if (l == r) return tree[rt].init(l);
        int mid = l + r >> 1;
        build(l, mid, rt << 1);
        build(mid + 1, r, rt << 1 | 1);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    void modify(int rt, int ll, int rr, int v) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].push(v);
        int mid = l + r >> 1;
        pushdown(rt);
        if (ll <= mid) modify(rt << 1, ll, rr, v);
        if (mid < rr) modify(rt << 1 | 1, ll, rr, v);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    int query(int rt, int ll, int rr) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].mi;
        int mid = l + r >> 1;
        pushdown(rt);
        int res = 1e18;
        if (ll <= mid) res = min(res, query(rt << 1, ll, rr));
        if (mid < rr) res = min(res, query(rt << 1 | 1, ll, rr));
        return res;
    }
}
namespace S3 {
    struct Node {
        int l, r, mx, tag;
        void init(int p) {
            l = r = p;
            mx = pre1[p] - a[p];
            tag = 0;
        }
        void push(int v) {
            mx += v, tag += v;
        }
    } tree[N << 2];
    Node operator+(const Node &l, const Node &r) {
        return {l.l, r.r, max(l.mx, r.mx), 0};
    }
    void pushdown(int rt) {
        if (tree[rt].tag) {
            tree[rt << 1].push(tree[rt].tag);
            tree[rt << 1 | 1].push(tree[rt].tag);
            tree[rt].tag = 0;
        }
    }
    void build(int l, int r, int rt) {
        if (l == r) return tree[rt].init(l);
        int mid = l + r >> 1;
        build(l, mid, rt << 1);
        build(mid + 1, r, rt << 1 | 1);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    void modify(int rt, int ll, int rr, int v) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].push(v);
        int mid = l + r >> 1;
        pushdown(rt);
        if (ll <= mid) modify(rt << 1, ll, rr, v);
        if (mid < rr) modify(rt << 1 | 1, ll, rr, v);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    int query(int rt, int ll, int rr) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].mx;
        int mid = l + r >> 1;
        pushdown(rt);
        int res = -1e18;
        if (ll <= mid) res = max(res, query(rt << 1, ll, rr));
        if (mid < rr) res = max(res, query(rt << 1 | 1, ll, rr));
        return res;
    }
}
namespace S4 {
    struct Node {
        int l, r, mx, tag;
        void init(int p) {
            l = r = p;
            mx = b[p] - pre2[p];
            tag = 0;
        }
        void push(int v) {
            mx += v, tag += v;
        }
    } tree[N << 2];
    Node operator+(const Node &l, const Node &r) {
        return {l.l, r.r, max(l.mx, r.mx), 0};
    }
    void pushdown(int rt) {
        if (tree[rt].tag) {
            tree[rt << 1].push(tree[rt].tag);
            tree[rt << 1 | 1].push(tree[rt].tag);
            tree[rt].tag = 0;
        }
    }
    void build(int l, int r, int rt) {
        if (l == r) return tree[rt].init(l);
        int mid = l + r >> 1;
        build(l, mid, rt << 1);
        build(mid + 1, r, rt << 1 | 1);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    void modify(int rt, int ll, int rr, int v) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].push(v);
        int mid = l + r >> 1;
        pushdown(rt);
        if (ll <= mid) modify(rt << 1, ll, rr, v);
        if (mid < rr) modify(rt << 1 | 1, ll, rr, v);
        tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    }
    int query(int rt, int ll, int rr) {
        int &l = tree[rt].l, &r = tree[rt].r;
        if (ll <= l && r <= rr) return tree[rt].mx;
        int mid = l + r >> 1;
        pushdown(rt);
        int res = -1e18;
        if (ll <= mid) res = max(res, query(rt << 1, ll, rr));
        if (mid < rr) res = max(res, query(rt << 1 | 1, ll, rr));
        return res;
    }
}
signed main() {
    cin.tie(0)->sync_with_stdio(false);
    int T;
    cin >> T;
    while (T--) {
        int n, q;
        cin >> n >> q;
        for (int i = 1; i <= n; ++i) cin >> a[i], b[i] = a[i];
        for (int i = 1; i <= n; ++i) a[i] -= i - 1;
        for (int i = 1; i <= n; ++i) b[i] += i - 1;
        int m1 = 0, m2 = 0;
        pre1[n + 1] = -1e18;
        for (int i = n; i; --i)
            pre1[i] = max(pre1[i + 1], a[i]);
        pre2[n + 1] = 1e18;
        for (int i = n; i; --i)
            pre2[i] = min(pre2[i + 1], b[i]);
        for (int i = 1; i <= n; ++i)
            m1 = max(m1, pre1[i] - a[i]);
        for (int i = 1; i <= n; ++i)
            m2 = max(m2, b[i] - pre2[i]);
        cout << max(m1, m2) << '\n';
        S1::build(1, n + 1, 1);
        S2::build(1, n + 1, 1);
        S3::build(1, n, 1);
        S4::build(1, n, 1);
        // S3: pre1 - a[i]
        // S4: b[i] - pre2
        while (q--) {
            int p, x;
            cin >> p >> x;
            int ap = a[p], bp = b[p];
            a[p] = x - p + 1;
            b[p] = x + p - 1;
            if (ap <= a[p]) {
                int l = 1, r = p, best = -1;
                while (l <= r) {
                    int mid = l + r >> 1;
                    if (S1::query(1, mid, mid) < a[p]) best = mid, r = mid - 1;
                    else l = mid + 1;
                }
                if (best != -1) {
                    ap = S1::query(1, p, p);
                    S3::modify(1, best, p, a[p] - ap);
                    S1::modify(1, best, p, a[p]);
                } 
                else S3::modify(1, p, p, S1::query(1, p, p) - a[p] - S3::query(1, p, p));
            } else {
                int l = 1, r = p, best = -1;
                while (l <= r) {
                    int mid = l + r >> 1;
                    if (S1::query(1, mid, mid) == ap) best = mid, r = mid - 1;
                    else l = mid + 1;
                }
                if (best != -1) {
                    int pp = S1::query(1, p + 1, p + 1);
                    pp = max(pp, a[p]);
                    ap = S1::query(1, p, p);
                    S3::modify(1, best, p, pp - ap);
                    S1::modify(1, best, p, pp);
                }
                else S3::modify(1, p, p, S1::query(1, p, p) - a[p] - S3::query(1, p, p));
            }
            if (bp >= b[p]) {
                int l = 1, r = p, best = -1;
                while (l <= r) {
                    int mid = l + r >> 1;
                    if (S2::query(1, mid, mid) > b[p]) best = mid, r = mid - 1;
                    else l = mid + 1;
                }
                if (best != -1) {
                    bp = S2::query(1, p, p);
                    S4::modify(1, best, p, bp - b[p]);
                    S2::modify(1, best, p, b[p]);
                } else 
                S4::modify(1, p, p, -S2::query(1, p, p) + b[p] - S4::query(1, p, p));
            } else {
                int l = 1, r = p, best = -1;
                while (l <= r) {
                    int mid = l + r >> 1;
                    if (S2::query(1, mid, mid) == bp) best = mid, r = mid - 1;
                    else l = mid + 1;
                }
                if (best != -1) {
                    int pp = S2::query(1, p + 1, p + 1);
                    pp = min(pp, b[p]);
                    bp = S2::query(1, p, p);
                    S4::modify(1, best, p, bp - pp);
                    S2::modify(1, best, p, pp);
                } else
                S4::modify(1, p, p, -S2::query(1, p, p) + b[p] - S4::query(1, p, p));
            }
            int m1 = S3::tree[1].mx;
            int m2 = S4::tree[1].mx;
            // for (int i = 1; i <= n; ++i)
            //     m1 = max(m1, S1::query(1, i, i) - a[i]);
            // for (int i = 1; i <= n; ++i)
            //     m2 = max(m2, b[i] - S2::query(1, i, i));
            // cout << max(m1, m2) << ' ' << m1 << ' ' << m2 << '\n';
            cout << max(m1, m2) << '\n';
        }
    }
    return 0;
}