minimum nr of adjacent swaps to mk arr2==arr1

#include <bits/stdc++.h>
using namespace std;
constexpr int NMAX = 1e5 + 3;
int n, arr1[NMAX], arr2[NMAX];
int posOfElemIn2nd[NMAX], posOfIthFrom1stIn2nd[NMAX];

void readArr(int arr[NMAX]) {
    for (int i = 1; i <= n; i++) {
        scanf("%d", arr + i);
    }
}

struct SegTree {
    int tree[4 * NMAX];

    void update(int node, int le, int ri, int val) {
        if (le == ri) {
            tree[node]++;
            return;
        }
        int mid = (le + ri) / 2;
        int leSon = node * 2, riSon = node * 2 + 1;
        if (val <= mid) {
            update(leSon, le, mid, val);
        } else {
            update(riSon, mid + 1, ri, val);
        }
        tree[node] = tree[leSon] + tree[riSon];
    }

    int query(int node,int le, int ri, int qle, int qri) {
        if (qle > ri || qri < le) {
            return 0;
        }
        if (qle <= le && ri <= qri) {
            return tree[node];
        }
        int mid = (le + ri) / 2;
        int leSon = node * 2, riSon = node * 2 + 1;
        int leAns = query(leSon, le, mid, qle, qri);
        int riAns = query(riSon, mid + 1, ri, qle, qri);
        return leAns + riAns;
    }
};

int main() {
    scanf("%d", &n);
    readArr(arr1);
    readArr(arr2);

    for (int i = 1; i <= n; i++) {
        posOfElemIn2nd[arr2[i]] = i;
    }
    for (int i = 1; i <= n; i++) {
        posOfIthFrom1stIn2nd[i] = posOfElemIn2nd[arr1[i]];
    }

    int ans = 0;
    SegTree segTree;
    for (int i = n; i > 0; i--) {
        ans += segTree.query(1, 1, n, 1, posOfIthFrom1stIn2nd[i]);
        segTree.update(1, 1, n, posOfIthFrom1stIn2nd[i]);
    }
    printf("%d\n", ans);
    return 0;
}