Language: C++

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

#define LL long long
#define LB long double
#define ull unsigned long long
#define x first
#define y second
#define pb push_back
#define pf push_front
#define mp make_pair
#define Pair pair<int,int>
#define pLL pair<LL,LL>
#define pii pair<double,double>
#define LOWBIT(x) x & (-x)
// #define LOCAL true

const int INF=2e9;
const LL LINF=2e16;
const int magic=348;
const int MOD=1e9+7;
const double eps=1e-10;
const double pi=acos(-1);

struct fastio
{
	static const int S=1e7;
	char rbuf[S+48],wbuf[S+48];int rpos,wpos,len;
	fastio() {rpos=len=wpos=0;}
	inline char Getchar()
	{
		if (rpos==len) rpos=0,len=fread(rbuf,1,S,stdin);
		if (!len) return EOF;
		return rbuf[rpos++];
	}
	template <class T> inline void Get(T &x)
	{
		char ch;bool f;T res;
		while (!isdigit(ch=Getchar()) && ch!='-') {}
		if (ch=='-') f=false,res=0; else f=true,res=ch-'0';
		while (isdigit(ch=Getchar())) res=res*10+ch-'0';
		x=(f?res:-res);
	}
	inline void getstring(char *s)
	{
		char ch;
		while ((ch=Getchar())<=32) {}
		for (;ch>32;ch=Getchar()) *s++=ch;
		*s='\0';
	}
	inline void flush() {fwrite(wbuf,1,wpos,stdout);fflush(stdout);wpos=0;}
	inline void Writechar(char ch)
	{
		if (wpos==S) flush();
		wbuf[wpos++]=ch;
	}
	template <class T> inline void Print(T x,char ch)
	{
		char s[20];int pt=0;
		if (x==0) s[++pt]='0';
		else
		{
			if (x<0) Writechar('-'),x=-x;
			while (x) s[++pt]='0'+x%10,x/=10;
		}
		while (pt) Writechar(s[pt--]);
		Writechar(ch);
	}
	inline void printstring(char *s)
	{
		int pt=1;
		while (s[pt]!='\0') Writechar(s[pt++]);
	}
}io;

template<typename T> inline void check_max(T &x,T cmp) {x=max(x,cmp);}
template<typename T> inline void check_min(T &x,T cmp) {x=min(x,cmp);}
template<typename T> inline T myabs(T x) {return x>=0?x:-x;}
template<typename T> inline T gcd(T x,T y) {return y==0?x:gcd(y,x%y);}
inline int add(int x) {if (x>=MOD) x-=MOD;return x;}
inline int add(int x,int MO) {if (x>=MO) x-=MO;return x;}
inline int sub(int x) {if (x<0) x+=MOD;return x;}
inline int sub(int x,int MO) {if (x<0) x+=MO;return x;}
inline void Add(int &x,int y) {x=add(x+y);}
inline void Add(int &x,int y,int MO) {x=add(x+y,MO);}
inline void Sub(int &x,int y) {x=sub(x-y);}
inline void Sub(int &x,int y,int MO) {x=sub(x-y,MO);}
template<typename T> inline int quick_pow(int x,T y) {int res=1;while (y) {if (y&1) res=1ll*res*x%MOD;x=1ll*x*x%MOD;y>>=1;}return res;}
template<typename T> inline int quick_pow(int x,T y,int MO) {int res=1;while (y) {if (y&1) res=1ll*res*x%MO;x=1ll*x*x%MO;y>>=1;}return res;}

const int MAXN=1000;
const int MAXM=2e5;

int n,m;
vector<Pair> v[MAXN+48];
vector<int> vv[MAXN+48];
bool visited1[MAXN+48],visited2[MAXN+48],visited3[MAXN+48],ok[MAXN+48];
int ans[MAXM+48];

inline void dfs1(int cur)
{
	visited1[cur]=true;
	for (register int i=0;i<int(vv[cur].size());i++)
	{
		register int y=vv[cur][i];
		if (!visited1[y]) dfs1(y);
	}
}

inline void dfs2(int cur)
{
	visited2[cur]=true;
	for (register int i=0;i<int(v[cur].size());i++)
	{
		register int y=v[cur][i].x;
		if (!visited2[y]) dfs2(y);
	}
}

int main ()
{
#ifdef LOCAL
	double TIME=clock();
	freopen ("a.in","r",stdin);
	freopen ("a.out","w",stdout);
	cerr<<"Running..."<<endl;
#endif
	io.Get(n);io.Get(m);int x,y;
	for (register int i=1;i<=m;i++)
	{
		io.Get(x);io.Get(y);
		v[x].pb(mp(y,i));vv[y].pb(x);
	}
	for (register int i=1;i<=n;i++)
	{
		memset(visited1,false,sizeof(visited1));
		memset(visited2,false,sizeof(visited2));
		memset(ok,false,sizeof(ok));
		dfs1(i);visited2[i]=true;
		for (register int j=0;j<int(v[i].size())-1;j++)
		{
			dfs2(v[i][j].x);
			for (register int k=j+1;k<int(v[i].size());k++)
				if (visited2[v[i][k].x]) ok[v[i][k].x]=true;
		}
		memset(visited2,false,sizeof(visited2));
		visited[2]=true;
		for (register int j=int(v[i].size())-1;j>=1;j--)
		{
			dfs2(v[i][j].x);
			for (register int k=j-1;k>=0;k--)
				if (visited2[v[i][k].x]) ok[v[i][k].x]=true;
		}
		for (register int j=0;j<int(v[i].size());j++) ans[v[i][j].y]=(visited1[v[i][j].x]^ok[v[i][j].x]);
	}
	for (register int i=1;i<=m;i++) printf(ans[i]?"diff\n":"same\n");
	io.flush();
#ifdef LOCAL
	cerr<<"Exec Time: "<<(clock()-TIME)/CLOCKS_PER_SEC<<endl;
#endif
	return 0;
}

Compiler output:
a.cc: In function 'void dfs1(int)':
a.cc:103:27: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  103 |         for (register int i=0;i<int(vv[cur].size());i++)
      |                           ^
a.cc:8:11: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
    8 | #define y second
      |           ^~~~~~
a.cc:105:30: note: in expansion of macro 'y'
  105 |                 register int y=vv[cur][i];
      |                              ^
a.cc: In function 'void dfs2(int)':
a.cc:113:27: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  113 |         for (register int i=0;i<int(v[cur].size());i++)
      |                           ^
a.cc:8:11: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
    8 | #define y second
      |           ^~~~~~
a.cc:115:30: note: in expansion of macro 'y'
  115 |                 register int y=v[cur][i].x;
      |                              ^
a.cc: In function 'int main()':
a.cc:129:27: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  129 |         for (register int i=1;i<=m;i++)
      |                           ^
a.cc:134:27: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  134 |         for (register int i=1;i<=n;i++)
      |                           ^
a.cc:140:35: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  140 |                 for (register int j=0;j<int(v[i].size())-1;j++)
      |                                   ^
a.cc:143:43: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  143 |                         for (register int k=j+1;k<int(v[i].size());k++)
      |                                           ^
a.cc:147:17: error: 'visited' was not declared in this scope; did you mean 'visited3'?
  147 |                 visited[2]=true;
      |                 ^~~~~~~
      |                 visited3
a.cc:148:35: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  148 |                 for (register int j=int(v[i].size())-1;j>=1;j--)
      |                                   ^
a.cc:151:43: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  151 |                         for (register int k=j-1;k>=0;k--)
      |                                           ^
a.cc:154:35: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  154 |                 for (register int j=0;j<int(v[i].size());j++) ans[v[i][j].y]=(visited1[v[i][j].x]^ok[v[i][j].x]);
      |                                   ^
a.cc:156:27: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
  156 |         for (register int i=1;i<=m;i++) printf(ans[i]?"diff\n":"same\n");
      |                           ^