159A - Friends or Not - CodeForces Solution

// ============================================================================ //
// ||                                                                        || //
// ||             International University of Business Agriculture           || //
// ||                    and Technology, DHaka, Bangladesh                   || //
// ||                           Emrul Hasan Emon                             || //
// ||                                                                        || //
// ============================================================================ //


///              B I S M I L L A H I R  R A H M A N I R  R A H I M


#include<bits/stdc++.h>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef bool                      boo;
typedef int                       li;
typedef long long int             ll;
typedef unsigned long long int    lu;
typedef double                    db;

//----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

typedef vector < li >                   vli;
typedef vector < ll >                   vll;
typedef set < li >                      sli;
typedef set < ll >                      sll;
typedef pair < pair<li, li>, li>        PLL;
typedef pair < ll, ll >                 pll;
typedef map < li,li >                   mli;
typedef map < ll,ll >                   mll;
typedef vector < pair < li, li > >      vpi;
typedef vector < pair < ll, ll > >      vpl;

//----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

#define tc                        int t;cin>>t;while(t--)
#define inp_i(a,n)                for(i=0; i<n ;i++) cin>>a[i]
#define out_i(a, b, c)            for(i=b; i<c; i++) cout<<a[i] spc; cout nl;
#define lp(i,a,b)                 for(i=a;i<b;i++)
#define len(z)                    z.begin(),z.end()
#define faster                    ios::sync_with_stdio(0); cin.tie(0);cout.tie(0);
#define input_txt                 freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define nl                        <<"\n"
#define spc                       <<" "
#define sp                        <<" "<<
#define co(x)                     cout<<x nl
#define sz(a)                     a.size()
#define cy                        cout<<"YES" nl
#define cn                        cout<<"NO" nl
#define pb                        push_back
#define F                         first
#define S                         second
#define pi                        2*acos(0.0)
#define clr(z)                    z.clear()
#define rn                        return
#define gcd(a,b)                  __gcd(a,b)
#define mem(b,z)                  memset(b,z,sizeof(b))
#define fixed(x)                  fixed<<setprecision(x)

//----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

template<typename T>
using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;

const double inf = 0.0000;
const int lx = 2e5 + 23;
const int mod = 1e9 + 7;
const int mxm = 1e8 + 3;

void solve()
{
   int n, d, i;
   cin >> n >> d;
   
   map<pair<string, string>, vector<int> > msg;
   map<pair<string, string>, int> frnd;
   
   frnd.clear();
   msg.clear();
   for(i = 0; i < n; i++)
   {
        string u, v;
        int t;
        cin >> u >> v >> t;
       
        if(frnd[{u, v}] or frnd[{v, u}]) continue;
       
        msg[{u, v}].push_back(t);
	
        int s1 = msg[{u, v}].size();
	int s2 = msg[{v, u}].size();
	
        for(int j = 0; j < s2; j++)
	{
	    int x = msg[{v, u}][j];
	    if(x < t and t-x <= d)
	    {
		frnd[{u, v}]++;
	    }
	}
   }
   int ans = 0;
   for(auto it : frnd) if(it.S > 0) ans++;
   cout << ans << '\n';
   for(auto it: frnd)
   {
       if(it.S > 0) cout << it.F.F << " " << it.F.S << '\n';
   }
}

void init_code()
{
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
}

int main()
{
    faster
    
    solve();
// A L H A M D U L I L L A H
// 1 2 3 2 1
}

//----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

/*
bool mark[lx];
vector<int> primes;

void sieve()
{
    mark[0] = mark[1] = true;
    
    for(int i = 3; i*i <= lx; i++)
    {
	if(!mark[i])
	{
	    for(int j = i*i; j < lx; j += i)
		mark[j] = true;
	}
    }
    
    primes.push_back(2);
    for(int i = 3; i < lx; i += 2)
    {
	if(!mark[i])
	{
	    primes.push_back(i);
	}
    }
}
* 
ll Big_Mod(ll a, ll b)
{
	if(!b) return 1;
	ll ans = Big_Mod(a, b/2);
	ans %= mod;
	ans *= ans;
	ans %= mod;
	
	if(b&1)
	{
		a %= mod;
		ans *= a;
		ans %= mod;
	}
	return ans;
}
* 
ll fact(ll n)
{
    ll ans=1;
    for(ll i=1; i<=n; i++)
        ans=(ans*i)%mod;
    return ans;
}

ll nCr(ll n, ll k)
{
    return fact(n)*1ll*Big_Mod(fact(k), mod-2)%mod*1ll*Big_Mod(fact(n-k), mod-2)%mod;
}

ll gcd(ll a, ll b)
{
    if (a == 0)
        return b;
    return gcd(b % a, a);
}

void number_of_divisors(li n)
{
    //Number of divisors of every number between 1 to n
    for(li i = 1; i*i <= n; i++)
    {
        for(li j = i*i; j <= n; j += i)
        {
            if(i*i == j)
                a[j]++;
            else
                a[j] += 2;
        }
    }
}

void sum_of_divisor()
{
    for(li i = 1; i * i <= 1e7; i++)
    {
        for(li j = i*i; j < 1e7; j += i)
        {
            if(j == i*i)
                a[j] += i;
            else
                a[j] += i+(j/i);
        }
    }
}

*/