【模板】动态主席树

如题，这是一个模板。。。

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <cctype>

inline void read(int & x)
{
    x = 0;
    int k = 1;
    char c = getchar();
    while (!isdigit(c))
        if (c == '-') c = getchar(), k = -1;
        else c = getchar();
    while (isdigit(c))
        x = (x << 1) + (x << 3) + (c ^ 48),
        c = getchar();
    x *= k;
}

struct Node
{
    int l, r, k, q;
}q[101010];

const int MAXN = 1010100 << 6;
int n, m, tot = 0, id = 0;
int a[MAXN], b[MAXN], ls[MAXN], rs[MAXN], sum[MAXN]; 
int T[MAXN], S[MAXN], use[MAXN];

char opt[11];

inline int lowbit(int x)
{
    return x & (-x);
}

inline int Lsh(int x)
{
    return std::lower_bound(a + 1, a + tot + 1, x) - a;
}

inline void Pushup(int u)
{
    sum[u] = sum[ls[u]] + sum[rs[u]];
}

int Build(int l, int r)
{
    int rt = ++id;
    sum[rt] = 0;
    if (l != r)
    {
        int mid = l + r >> 1;
        ls[rt] = Build(l, mid);
        rs[rt] = Build(mid + 1, r);
    }
    return rt;
}

int Add(int pre, int l, int r, int x, int cm)
{
    int rt = ++id;
    ls[rt] = ls[pre],
    rs[rt] = rs[pre],
    sum[rt] = sum[pre] + cm;
    if (l < r)
    {
        int mid = l + r >> 1;
        if (x <= mid)
            ls[rt] = Add(ls[pre], l, mid, x, cm);
        else 
            rs[rt] = Add(rs[pre], mid + 1, r, x, cm);
    }
    return rt;
}

inline void Modify(int u, int pos, int x)
{
    while (u <= n)
    {
        S[u] = Add(S[u], 1, tot, pos, x);
        u += lowbit(u);
    }
}

inline int Sum(int u)
{
    int ans = 0;
    while (u > 0)
    {
        ans += sum[ls[use[u]]];
        u -= lowbit(u);
    }
    return ans;
}

int Query(int u, int v, int ur, int vr, int l, int r, int k)
{
    if (l >= r) return l;
    int mid = l + r >> 1;
    int df = Sum(v) - Sum(u) + sum[ls[vr]] - sum[ls[ur]];
    if (k <= df)
    {
        for (int i = u; i; i -= lowbit(i))
            use[i] = ls[use[i]];
        for (int i = v; i; i -= lowbit(i))
            use[i] = ls[use[i]];
        return
            Query(u, v, ls[ur], ls[vr], l, mid, k);
    }
    else
    {
        for (int i = u; i; i -= lowbit(i))
            use[i] = rs[use[i]];
        for (int i = v; i; i -= lowbit(i))
            use[i] = rs[use[i]];
        return
            Query(u, v, rs[ur], rs[vr], mid + 1, r, k - df);
    }
}

signed main()
{
    read(n), read(m);
    for (int i = 1; i <= n; ++i)
        read(b[i]), a[++tot] = b[i];
    for (int i = 1; i <= m; ++i)
    {
        scanf("%s", opt);
        if (opt[0] == 'Q')
            read(q[i].l), read(q[i].r), read(q[i].k), q[i].q = 1;
        else 
            read(q[i].l), read(q[i].r), q[i].q = 0,
            a[++tot] = q[i].r;
    }
    std::sort(a + 1, a + tot + 1);
    int cur = std::unique(a + 1, a + tot + 1) - a - 1;
    tot = cur;
    T[0] = Build(1, tot);
    for (int i = 1; i <= n; ++i)
        T[i] = Add(T[i - 1], 1, tot, Lsh(b[i]), 1);
    for (int i = 1; i <= n; ++i)
        S[i] = T[0];
    for (int i = 1; i <= m; ++i)
        if (q[i].q)
        {
            for (int j = q[i].l - 1; j; j -= lowbit(j))
                use[j] = S[j];
            for (int j = q[i].r; j; j -= lowbit(j))
                use[j] = S[j];
            printf("%d\n", a[Query(q[i].l - 1, q[i].r, T[q[i].l - 1], T[q[i].r], 1, tot, q[i].k)]);
        }
        else
        {
            Modify(q[i].l, Lsh(b[q[i].l]), -1);
            Modify(q[i].l, Lsh(q[i].r), 1);
            b[q[i].l] = q[i].r;
        }
    return 0;
}