我看好多题解离散化都是这样

bool cmp(point q, point w){
    if (q.val == w.val)
        return q.num < w.num;
    return q.val < w.val;
}

但是本人这样离散化也可以通过,研究了一下不知道原因,还请各位大佬帮帮忙

signed main() {
    cin >> n; int ans = 0;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        b[i] = a[i];
    }
    sort(b + 1, b + n + 1);
    for (int i = 1; i <= n; i++) {
        a[i] = lower_bound(b + 1, b + n + 1, a[i]) - b;
    }
    //前
   /* for (int i = 1; i <= n; i++) {
        add(a[i], 1);
        ans += i - sum(a[i]);
    }*/
    //后
    for (int i = n; i >= 1; i--) {
        add(a[i], 1);
        ans += sum(a[i]-1);
    }
    cout << ans << endl;
}