我同学拿了 60pts 的代码，感觉时间复杂度不太正常，求分析

#include <bits/stdc++.h>
#pragma GCC optimize(1)
#pragma GCC optimize(2)
#pragma GCC optimize(3, "Ofast", "inline")
#define pii pair<int, int>
#define Nxt puts("")
#define Spa putchar(32)
#define Pline puts("------------------------------")
namespace FastIO {
int write_top, read_f, read_x;
char read_char;
int write_st[20];
inline int read(int &a) {
    read_char = getchar();
    read_f = 1;
    a = 0;
    while (!isdigit(read_char)) {
        if (read_char == '-')
            read_f = -1;
        read_char = getchar();
    }
    while (isdigit(read_char)) {
        a = (a << 1) + (a << 3) + (read_char ^ 48);
        read_char = getchar();
    }
    return a = a * read_f;
}
inline int read() {
    read_char = getchar();
    read_f = 1;
    read_x = 0;
    while (!isdigit(read_char)) {
        if (read_char == '-')
            read_f = -1;
        read_char = getchar();
    }
    while (isdigit(read_char)) {
        read_x = (read_x << 1) + (read_x << 3) + (read_char ^ 48);
        read_char = getchar();
    }
    return read_x * read_f;
}
inline void write(int x) {
    if (x < 0)
        putchar('-'), x = -x;
    write_top = 0;
    do {
        write_st[++write_top] = x % 10;
        x /= 10;
    } while (x);
    while (write_top) putchar(write_st[write_top--] + '0');
    return;
}
inline void tomax(int &a, int b) {
    if (a < b)
        a = b;
    return;
}
inline void tomin(int &a, int b) {
    if (a > b)
        a = b;
    return;
}
}  // namespace FastIO
using namespace FastIO;
using namespace std;
const int N = 1e6 + 5;
int n, m, ans;
int a[N], b[N];
bool flag[N];
set<pii> st;
struct Segment_tree {
    int mx[N << 2], pmx[N << 2];
    int mi[N << 2], pmi[N << 2];
#define ls p << 1
#define rs p << 1 | 1
#define mid (l + r >> 1)
    void pushup(int p) {
        mx[p] = max(mx[ls], mx[rs]);
        if (mx[p] == mx[ls])
            pmx[p] = pmx[ls];
        else
            pmx[p] = pmx[rs];
        mi[p] = min(mi[ls], mi[rs]);
        if (mi[p] == mi[ls])
            pmi[p] = pmi[ls];
        else
            pmi[p] = pmi[rs];
    }
    void build(int p, int l, int r) {
        if (l == r) {
            mx[p] = mi[p] = a[l];
            pmx[p] = pmi[p] = l;
            return;
        }
        build(ls, l, mid), build(rs, mid + 1, r);
        pushup(p);
    }
    void change(int p, int l, int r, int x) {
        if (l == r) {
            mx[p] = mi[p] = (flag[l] ? b[l] : a[l]);
            return;
        }
        if (mid >= x)
            change(ls, l, mid, x);
        else
            change(rs, mid + 1, r, x);
        pushup(p);
    }
} Set;
bool vis(int mx, int mi) {
    pii tmp = { mx, mi };
    auto it = st.lower_bound(tmp);
    if ((it == st.end()) || (*it != tmp)) {
        st.insert(tmp);
        return false;
    }
    return true;
}
void dfs(int p, int pre) {
    if (p == m + 1)
        return;
    if (vis(Set.mx[1], Set.mi[1]))
        return;
    //翻最大值
    int tmp = Set.pmx[1];
    if (pre != tmp) {
        if (flag[tmp] == 1 && b[tmp] > a[tmp]) {  //此时 b 朝上，反过来最大值减小
            flag[tmp] = 0;
            Set.change(1, 1, n, tmp);
            tomin(ans, Set.mx[1] - Set.mi[1]);
            dfs(p + 1, tmp);
            flag[tmp] = 1;
            Set.change(1, 1, n, tmp);
        } else if (flag[tmp] == 0 && a[tmp] > b[tmp]) {  //此时 a 朝上，反过来最大值减小
            flag[tmp] = 1;
            Set.change(1, 1, n, tmp);
            tomin(ans, Set.mx[1] - Set.mi[1]);
            dfs(p + 1, tmp);
            flag[tmp] = 0;
            Set.change(1, 1, n, tmp);
        }
    }
    //翻最小值
    tmp = Set.pmi[1];
    if (pre != tmp) {
        if (flag[tmp] == 1 && b[tmp] < a[tmp]) {  //此时 b 朝上，反过来最小值增大
            flag[tmp] = 0;
            Set.change(1, 1, n, tmp);
            tomin(ans, Set.mx[1] - Set.mi[1]);
            dfs(p + 1, tmp);
            flag[tmp] = 1;
            Set.change(1, 1, n, tmp);
        } else if (flag[tmp] == 0 && a[tmp] < b[tmp]) {  //此时 a 朝上，反过来最小值增大
            flag[tmp] = 1;
            Set.change(1, 1, n, tmp);
            tomin(ans, Set.mx[1] - Set.mi[1]);
            dfs(p + 1, tmp);
            flag[tmp] = 0;
            Set.change(1, 1, n, tmp);
        }
    }
}
signed main() {
    read(n), read(m);
    for (int i = 1; i <= n; i++) read(a[i]);
    for (int i = 1; i <= n; i++) read(b[i]);
    Set.build(1, 1, n);
    ans = Set.mx[1] - Set.mi[1];
    dfs(1, 0);
    write(ans);
}