C++ "Sắp xếp Insert"

#include<iostream>
using namespace std;

int *a, n;

void insert_sort(int *a, int n){
    for ( int k = 1; k < n; k++){
        // a1 <= a2 <= ... <= a[k-1];
        int key = a[k];
        for (int j = k-1; j >= 0; j--){
            if (key < a[j]) a[j+1] = a[j];
            else {
                a[j+1] = key;
                break;
            }
            if ( j == 0) a[j] = key;
        }
    }
}

int main(){
    cout << "n = "; cin >> n;
    a = new int[n];
    for (int i = 0; i < n; i++){
        cout << "a[" << i + 1 << "] = ";
        cin >> a[i];
    }
    insert_sort(a,n);
    for (int i = 0; i < n; i++)
        cout << a[i] << " ";
    delete[] a;
    return 0;

}