#include <bits/stdc++.h>
using namespace std;
long n,a[1000],x,y,d=0;
int main() {
    cout << "Nhap do dai mang: "; cin >> n;
    cout << "Nhap X: "; cin >> x;
    for (long i=0; i<n; i++) {
        cin >> a[i];
        if (a[i]==x) d++;
    }
    cout << "So lan xuat hien cua " << x << " trong mang A la: " << d << endl;
    cout << "So lan xuat hien cua tung phan tu trong mang la: \n";
    for (long i=0; i<n; i++) {
        d=0;
        for (long j=0; j<n; j++) if (a[i]==a[j]) d++;
        cout << " @ Phan tu " << a[i] << " xuat hien " << d << " lan.\n";
    }
    cout << "Nhap X: "; cin >> x;
    cout << "Nhap Y: "; cin >> y;
    cout << "Vi tri xuat hien cua " << x << " trong mang la: "; for (long i=0; i<n; i++) if (a[i]==x) {
        cout << i << " ";
        a[i]=y;
    } cout << endl;
    cout << "Mang sau khi thay " << x << " thanh " << y << ": "; for (long i=0; i<n; i++) cout << a[i] << " ";
}

n = int(input('N='))
a = [0]*n
for i in range (n):
    a[i] = int(input('A[%d]='%i))
x = int(input('X='))
print('so lan xuat hien cua X:',a.count(x))
b = set(a)
for i in b:
    print('so lan xuat hien cua',i,':',a.count(i))
_x = int(input('X='))
y = int(input('y='))
print('vi tri xuat hien cua x:',end=' ')
for i in range (n):
    if (a[i] == _x):
        print(i, end=' ')
        a[i] = y
print()
print('mang a sau khi thay the gia tri x thanh y:',*a)

$\\$

`@Daoanhviet96`