Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của flashmt

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
const int base = 1000000007;

int main()
{
    int n,a[100100];
    long long ans=1;
    cin >> n;
    for (int i=0;i<n;i++) scanf("%d",a+i);
    sort(a,a+n);
    for (int i=0;i<n;i++) ans=ans*(a[i]-i)%base;
    cout << ans << endl;
}

Code mẫu của happyboy99x

#include<cstdio>
#include<algorithm>
using namespace std;

#define MOD 1000000007
#define N 100000

int a[N], n;

int main() {
    scanf("%d", &n);
    for(int i = 0; i < n; ++i) scanf("%d", a+i);
    sort(a, a+n);
    long long res = 1;
    for(int i = 0; i < n; ++i) res = res * (a[i] - i) % MOD;
    printf("%lld\n", res);
    return 0;
}

Code mẫu của ladpro98

program c11id;
uses    math;
const   fi='';
        k=1000000007;
var     res:int64;
        a:array[1..100001] of longint;
        inp:text;
        n,i:longint;

procedure input;
var     i:longint;
begin
        assign(inp,fi);
        reset(inp);
        readln(inp,n);
        for i:=1 to n do readln(inp,a[i]);
        close(inp);
end;


procedure swap(i,j:longint);
var     t:longint;
begin
        t:=a[i];
        a[j]:=a[i];
        a[i]:=a[j];
end;

procedure sort(l,r:longint);
var     pivot:longint;
        i,j:longint;
begin
        if l>=r then exit;
        pivot:=a[random(r-l+1)+l];
        i:=l;j:=r;
        repeat
                while a[i]<pivot do inc(i);
                while a[j]>pivot do dec(j);
                if i<=j then
                begin
                        if i<j then swap(i,j);
                        inc(i);
                        dec(j);
                end;

        until i>j;
        sort(l,j);
        sort(i,r);
end;


begin
        input;
        sort(1,n);
        res:=1;
        for i:=1 to n do
        begin
                res:=(res*((a[i]-i+1) mod k)) mod k;
        end;
        write(res);

end.

Code mẫu của RR

#include <sstream>
#include <iomanip>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <string>
#include <deque>
#include <complex>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define FORN(i,a,b) for(int i=(a),_b=(b);i<_b;i++)
#define DOWN(i,a,b) for(int i=a,_b=(b);i>=_b;i--)
#define SET(a,v) memset(a,v,sizeof(a))
#define sqr(x) ((x)*(x))
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair

#define DEBUG(x) cout << #x << " = "; cout << x << endl;
#define PR(a,n) cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl;
#define PR0(a,n) cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl;
using namespace std;

//Buffer reading
int INP,AM,REACHEOF;
#define BUFSIZE (1<<12)
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp) { \
        if (REACHEOF) return 0;\
        memset(BUF,0,sizeof BUF);\
        int inpzzz = fread(BUF,1,BUFSIZE,stdin);\
        if (inpzzz != BUFSIZE) REACHEOF = true;\
        inp=BUF; \
    } \
    INP=*inp++; \
}
#define DIG(a) (((a)>='0')&&((a)<='9'))
#define GN(j) { \
    AM=0;\
    GETCHAR(INP); while(!DIG(INP) && INP!='-') GETCHAR(INP);\
    if (INP=='-') {AM=1;GETCHAR(INP);} \
    j=INP-'0'; GETCHAR(INP); \
    while(DIG(INP)){j=10*j+(INP-'0');GETCHAR(INP);} \
    if (AM) j=-j;\
}
//End of buffer reading

const long double PI = acos((long double) -1.0);

bool isPrime(int n) {
    for(int i = 2; i*i <= n; ++i)
        if (n % i == 0) return false;
    return true;
}

int n, a[100111];

int main() {
    int k = 1000000000;
    while (!isPrime(k))
        ++k;
    while (scanf("%d", &n) == 1) {
        FOR(i,1,n) scanf("%d", &a[i]);
        sort(a+1, a+n+1);

        long long res = 1;
        FOR(i,1,n)
            if (a[i] - i + 1 <= 0) res = 0;
        if (res == 0) {
            cout << res << endl;
        }
        else {
            FOR(i,1,n)
                res = (res * (a[i] - i + 1)) % k;
            cout << res << endl;
        }
    }
    return 0;
}

Code mẫu của hieult

#include <set>
#include <map>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <ctime>
#include <deque>
#include <bitset>
#include <cctype>
#include <utility>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned int ui;
typedef unsigned long long ull;

#define Rep(i,n) for(int i = 0; i < (n); ++i)
#define Repd(i,n) for(int i = (n)-1; i >= 0; --i)
#define For(i,a,b) for(int i = (a); i <= (b); ++i)
#define Ford(i,a,b) for(int i = (a); i >= (b); --i)
#define Fit(i,v) for(__typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i)
#define Fitd(i,v) for(__typeof((v).rbegin()) i = (v).rbegin(); i != (v).rend(); ++i)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define ms(a,x) memset(a, x, sizeof(a))

template<class F, class T> T convert(F a, int p = -1) {
    stringstream ss;
    if (p >= 0)
        ss << fixed << setprecision(p);
    ss << a;
    T r;
    ss >> r;
    return r;
}
template<class T> T gcd(T a, T b) {
    T r;
    while (b != 0) {
        r = a % b;
        a = b;
        b = r;
    }
    return a;
}
template<class T> T lcm(T a, T b) {
    return a / gcd(a, b) * b;
}
template<class T> T sqr(T x) {
    return x * x;
}
template<class T> T cube(T x) {
    return x * x * x;
}
template<class T> int getbit(T s, int i) {
    return (s >> i) & 1;
}
template<class T> T onbit(T s, int i) {
    return s | (T(1) << i);
}
template<class T> T offbit(T s, int i) {
    return s & (~(T(1) << i));
}
template<class T> int cntbit(T s) {
    return s == 0 ? 0 : cntbit(s >> 1) + (s & 1);
}

const int bfsz = 1 << 16;
char bf[bfsz + 5];
int rsz = 0;
int ptr = 0;
char gc() {
    if (rsz <= 0) {
        ptr = 0;
        rsz = (int) fread(bf, 1, bfsz, stdin);
        if (rsz <= 0)
            return EOF;
    }
    --rsz;
    return bf[ptr++];
}
void ga(char &c) {
    c = EOF;
    while (!isalpha(c))
        c = gc();
}
int gs(char s[]) {
    int l = 0;
    char c = gc();
    while (isspace(c))
        c = gc();
    while (c != EOF && !isspace(c)) {
        s[l++] = c;
        c = gc();
    }
    s[l] = '\0';
    return l;
}
template<class T> bool gi(T &v) {
    v = 0;
    char c = gc();
    while (c != EOF && c != '-' && !isdigit(c))
        c = gc();
    if (c == EOF)
        return false;
    bool neg = c == '-';
    if (neg)
        c = gc();
    while (isdigit(c)) {
        v = v * 10 + c - '0';
        c = gc();
    }
    if (neg)
        v = -v;
    return true;
}

typedef pair<int, int> II;
const ld PI = acos(-1.0);
const ld eps = 1e-9;
const int dr[] = { -1, 0, +1, 0};
const int dc[] = { 0, +1, 0, -1};
const int inf = (int) 1e9 + 5;
const ll linf = (ll) 1e16 + 5;
const int mod = (ll) (1e9 + 7 + eps);
#define ok puts("ok")
#define maxn 1000005
#define maxe 40005

int n, a[maxn];

bool check_prime(ll x){
    for(int i = 2; i * i <= x; i++) if(x % i == 0) return false;
    return true;
}

int main(){
//  freopen("in.txt", "r", stdin);

    ll MOD = 1000000000;
    while(!check_prime(MOD)) MOD++;

    scanf("%d", &n); Rep(i, n) scanf("%d", &a[i]);
    sort(a, a + n);
    ll res = 1;
    Rep(i, n) res = res * (a[i] - i) % mod;
    cout << res;

    return 0;

}

Code mẫu của skyvn97

#include<stdio.h>
#define MAX   100100
#define MOD   1000000007
typedef unsigned long long ull;
ull a[MAX];
ull i,n,t;
ull min(ull x, ull y)
{
    if (x>y) return(y); else return(x);
}
void merge(ull a[],ull left, ull mid, ull right)
{
    ull b[MAX];
    ull c[MAX];
    ull i,ib,ic;
    for (i=1;i<=mid-left+1;i=i+1) b[i]=a[i+left-1];
    for (i=1;i<=right-mid;i=i+1) c[i]=a[i+mid];
    ib=1; ic=1;
    for (i=left;i<=right;i=i+1)
        {
            if (ib>mid-left+1) a[i]=c[ic];
            else
                if (ic>right-mid) a[i]=b[ib];
                else a[i]=min(b[ib],c[ic]);
            if (a[i]==b[ib]) ib=ib+1; 
            else ic=ic+1;
        }
}
void mergesort(ull a[],ull left,ull right)
{   
    if (right<=left) return;
    ull mid=(right+left)/2;
    mergesort(a,left,mid);
    mergesort(a,mid+1,right);
    merge(a,left,mid,right);
}
int main(void)
{
    scanf("%llu",&n);
    for (i=1;i<=n;i=i+1) scanf("%llu",&a[i]);
    mergesort(a,1,n);
    t=1;
    for (i=1;i<=n;i=i+1) t=(t*(a[i]-i+1))%MOD;
    printf("%llu",t);        
}