Language: C++

#include <bits/stdc++.h>
using namespace std;

typedef long double LD;
typedef long long ll;
typedef map<int,int> mii;
typedef pair<int,int> pii;
typedef vector<pii> vpii;

#define pb              push_back
#define mp              make_pair
#define F               first
#define S               second
#define mod             1000000007
#define INF             2147483647
#define Endl            "\n"
#define FasterIO        ios_base::sync_with_stdio(0);cin.tie(0); cout.tie(0) ;
#define precision(a)    cout << fixed << setprecision(a)
#define bug(a,b)        cout<<a<<"\t"<<b<<"\n";
#define Case(a,b)       cout<<"Case "<<a<<": "<<b<<"\n";
#define reset(a,b)      memset(a,b,sizeof(a));
#define srt(a)      sort(a.begin(),a.end());

const int MAXN = 1000005;
const int SQRTN = 1003;
const int LOGN = 22;
const double PI=acos(-1);
const int sz=1e5+9;

int strtoint(string str){
    stringstream ss(str);
    int x = 0;
    ss >> x ;
    return x ;
}
string intostr(int x){
    stringstream ss;
    ss << x;
    string str = ss.str();
    return str;
}
void rem(string &s, const string &c) {
	auto pos = s.find(c);
	if (pos == string::npos) {
		cout << -1 << endl;
		exit(0);
	}
	s.erase(0, pos + 1);
}
void println (int n){
    cout<<n<<"\n";
}
void printvec(vector <int> &a){
    for (int i=0;i<a.size();i++){
        cout<<a[i]<<" ";
    }
    cout<<"\n";
}

void printgraph(vector <int> g[],int e){
    for (int i=0;i<e;i++){
        cout<<i<<" --> ";
        for (int j=0;j<g[i].size();j++){
            cout<<g[i][j]<<" ";
        }
        cout<<"\n";
    }
}

void printmap (map <int,int> &mymap){
    for (auto itr = mymap.begin(); itr != mymap.end(); ++itr) {
        cout << '\t' << itr->first
             << '\t' << itr->second << '\n';
    }
    cout << "\n";
}

int a[MXN][4], dp[MXN][4];
int N;

int rec(int pos, int type){

    if(pos>N) return 0;

    if(dp[pos][type]!=-1) return dp[pos][type];

    int ret = -1;
    for(int i=1; i<=3; i++)
        if(i!=type)
            ret = max (ret, rec(pos+1,i) + a[pos+1][i]);

    return dp[pos][type] = ret;
}


void solve(){
    memset(dp,-1,sizeof(dp));
    int i,j;
    cin>>N;
    for(i=1; i<=N; i++)
        for(j=1; j<=3; j++)
            cin>>a[i][j];


   cout<< rec(0,0) << "\n";

    //printvec(v);
}


int main(){
    //FasterIO;

    solve();
    return 0;
}

Compiler output:
a.cc:78:7: error: 'MXN' was not declared in this scope; did you mean 'MAXN'?
   78 | int a[MXN][4], dp[MXN][4];
      |       ^~~
      |       MAXN
a.cc:78:19: error: 'MXN' was not declared in this scope; did you mean 'MAXN'?
   78 | int a[MXN][4], dp[MXN][4];
      |                   ^~~
      |                   MAXN
a.cc: In function 'int rec(int, int)':
a.cc:85:8: error: 'dp' was not declared in this scope; did you mean 'dup'?
   85 |     if(dp[pos][type]!=-1) return dp[pos][type];
      |        ^~
      |        dup
a.cc:90:44: error: 'a' was not declared in this scope
   90 |             ret = max (ret, rec(pos+1,i) + a[pos+1][i]);
      |                                            ^
a.cc:92:12: error: 'dp' was not declared in this scope; did you mean 'dup'?
   92 |     return dp[pos][type] = ret;
      |            ^~
      |            dup
a.cc: In function 'void solve()':
a.cc:97:12: error: 'dp' was not declared in this scope; did you mean 'dup'?
   97 |     memset(dp,-1,sizeof(dp));
      |            ^~
      |            dup
a.cc:102:18: error: 'a' was not declared in this scope
  102 |             cin>>a[i][j];
      |                  ^