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4 - Graph/Graph Traversal/FloodFill-Finding Connected Components/UVa-459-Graph-Connectivity[BFS].cpp

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+/**         In the name of Allah, the Gracious, the Merciful.
+*                 Praise be to Allah, Lord of the Worlds.
+*                 **************************************
+*
+*      I have not failed, I have just found 1000 WAYS that won't work.
+*        © كُودٌ قد حَوى دررًا بعينِ الحسنِ ملحوظة .. لِهذا قُلتُ تنبيهًا حقوقُ النقلِ محفوظة
+*
+*                   __________________________________
+*                    @Author : Abd El-Twab  M. Fakhry
+*                   __________________________________
+*/
+
+#pragma GCC optimize ("Ofast")
+
+#if __cplusplus >= 201402L
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+#include <ext/rope>
+#endif
+#include "bits/stdc++.h"
+
+#define  rforeach(_it, c)    for(__typeof((c).rbegin()) _it = (c).rbegin(); _it != (c).rend(); ++_it)
+#define  foreach(_it, c)     for(__typeof((c).begin()) _it = (c).begin(); _it != (c).end(); ++_it)
+#define  dbg(x)              cerr << #x << " = " << (x) << endl;
+#define  all(a)              (a).begin(), (a).end()
+#define  sz(a)               (int)a.size()
+#define  endl                '\n'
+
+using namespace std;
+#if __cplusplus >= 201402L
+using namespace __gnu_cxx;
+using namespace __gnu_pbds;
+#endif
+
+typedef unsigned long long  ull;
+typedef long double         lld;
+typedef __uint128_t        ulll;
+typedef long long            ll;
+typedef __int128            lll;
+
+/**---------------------->>  Constants  <<-----------------------**/
+
+const double    Pi      = 2 * acos(0.0),    Euler = 2.71828182845904523536;
+const double    Epsln   = 1e-9,           GoldenR = (1 + sqrtl(5.0)) / 2;
+const int       Mod     = (int)1e9 + 7,        oo = 0x3f3f3f3f;
+
+/**---------------->>  Functions & Shortcuts  <<-----------------**/
+
+#if __cplusplus >= 201402L
+mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
+template <class T> T rnd_in_rng(T a, T b)
+{ return uniform_int_distribution <ll> (a, b)(rng); /** [a, b] **/}
+
+template <class T> string to_string(T x)
+{
+    int sn = 1; if(x < 0) sn = -1, x *= sn; string s = "";
+    do { s = "0123456789"[x % 10] + s, x /= 10; } while(x);
+    return (sn == -1 ? "-" : "") + s;
+}
+
+auto str_to_int(string x)
+{
+    ulll ret = (x[0] == '-' ? 0 : x[0] - '0');
+    for(int i = 1; i < sz(x); ++i) ret = ret * 10 + (x[i] - '0');
+    return (x[0] == '-' ? -1 * (lll)ret : ret);
+}
+
+istream & operator >> (istream & in, lll & i) noexcept { string s; in >> s; i = str_to_int(s); return in; }
+ostream & operator << (ostream & os, const lll i) noexcept { os << to_string(i); return os; }
+istream & operator >> (istream & in, ulll & i) noexcept { string s; in >> s; i = str_to_int(s); return in; }
+ostream & operator << (ostream & os, const ulll i) noexcept { os << to_string(i); return os; }
+
+template <class T> T Unique(T v) { return v.erase(unique(all(v)), v.end()), v; }
+template <class T> T ExGcd(T a, T b, T & x, T & y)
+{
+    if(!a) { x = 0, y = 1; return b; }
+    T xx, yy, g = ExGcd(b % a, a, xx, yy);
+    x = yy - b / (lll)a * xx; y = xx;
+    return g;
+}
+
+/** Phi(a * b) = Phi(a) * Phi(b) where a and b Prime Factors and k their power **/
+template <class T> auto Phi(T a, int k) { return (lll)pow(a, k - 1) * (a - 1); }
+template <class T> T    Normal(T n) { n %= Mod; (n < 0) && (n += Mod); return n; }
+template <class T> T    ModMulInv(T a) { T x, y; assert(ExGcd(a, Mod, x, y) == 1); return Normal(x); }
+template <class T> T    Gcd(T a, T b) { return b ? Gcd(b, a % b) : a; }
+template <class T> auto Lcm(T a, T b) { return a / (lll)Gcd(a, b) * b; }
+
+/** Modular Calculations **/
+template <class T> auto _add(T a, T b, T Mod) { return (lll)a + b >= Mod ? (lll)a + b - Mod : a + b; }
+template <class T> T    _sub(T a, T b) { return a - b < 0 ? a - b + Mod : a - b; }
+template <class T> T    _mul(T a, T b) { return T((lll)a * b % Mod); }
+template <class T> T    _div(T a, T b) { return _mul(a, ModMulInv(b)); }
+template <class T> T    ModExp(T a, T n)
+{
+    a %= Mod; T result = 1;
+    while(n) { if(n & 1) result = _mul(result, a); a = _mul(a, a);  n >>= 1; }
+    return result;
+}
+
+template <class T> using indexed_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update >;
+template <class T> using min_heap = priority_queue < T, vector <T>, greater <T> >;
+
+template <typename F, typename S>
+ostream & operator << (ostream & os, const pair <F, S> & p)
+{ return os << "(" << p.first << ", " << p.second << ")"; }
+
+template <typename F, typename S>
+ostream & operator << (ostream & os, const map <F, S> & _mp)
+{ os << "["; foreach(it, _mp) { if(it != _mp.begin()) os << ", "; os << it->first << " = " << it->second; } return os << "]"; }
+
+template <typename T>
+ostream & operator << (ostream & os, const vector <T> & _v)
+{ os << "["; foreach(it, _v) { if(it != _v.begin()) os << ", "; os << *it; } return os << "]"; }
+
+template <typename T>
+ostream & operator << (ostream & os, const set <T> & _st)
+{ os << "["; foreach(it, _st) { if(it != _st.begin() ) os << ", "; os << *it; } return os << "]"; }
+
+template <typename T, size_t S>
+ostream & operator << (ostream & os, const array <T, S> & _ar)
+{ os << "["; foreach(it, _ar) { if(it != _ar.begin() ) os << ", "; os << *it; } return os << "]"; }
+
+template <typename T>
+ostream & operator << (ostream & os, const indexed_set <T> & _ist)
+{ os << "["; foreach(it, _ist) { if(it != _ist.begin() ) os << ", "; os << "(" << _ist.order_of_key(*it) << ", " << *it << ")"; } return os << "]"; }
+
+template <typename T> void write(T _begin, T _end)
+{ for(auto i = _begin; i != _end; ++i) cout << (*i) << ' '; cout << endl; }
+
+template <typename T> void read(T _begin, T _end)
+{ for(auto i = _begin; i != _end; ++i) cin >> (*i); }
+#endif
+
+const int dx[] = { 1, -1, 0, 0, 1, 1, -1, -1 };
+const int dy[] = { 0, 0, 1, -1, 1, -1, 1, -1 };
+const char dir[] = {'U', 'D', 'R', 'L'};
+
+void Fast() { cin.sync_with_stdio(0); cin.tie(0); cout.tie(0); }
+void File()
+{
+    #ifndef ONLINE_JUDGE
+    freopen("input.in", "r", stdin);
+    //freopen("output.out", "w", stdout);
+    #endif
+}
+
+const int N = (int)1e5 + 9, M = (int)1e6 + 9;
+
+/**------------------>>  Initialization gap  <<------------------**/
+
+int Head[30], Next[M], To[M], ne, CCs;
+bool vis[30];
+char u, v, en;
+string line;
+stringstream ss;
+
+void addEdge(int from, int to)
+{
+    Next[++ne] = Head[from];
+    Head[from] = ne;
+    To[ne] = to;
+}
+
+void BFS(int src)
+{
+    queue <int> q; q.push(src);
+    vis[src] = true;
+
+    int u;
+    while(q.size())
+    {
+        u = q.front(); q.pop();
+        for(int i = Head[u]; i; i = Next[i]) if(!vis[To[i]])
+        {
+            vis[To[i]] = true;
+            q.push(To[i]);
+        }
+    }
+}
+
+void _clear()
+{
+    memset(Head, 0x00, sizeof Head);
+    memset(vis, 0x00, sizeof vis);
+    ss.clear();
+    ne = CCs = 0;
+}
+
+void Solve()
+{
+    _clear();
+    getline(cin, line);
+    ss.str(line);
+    ss >> en; en -= 64;
+
+    while(getline(cin, line))
+    {
+        ss.clear();
+        ss.str(line);
+        if(!(ss >> u >> v)) break;
+        addEdge(u - 64, v - 64);
+        addEdge(v - 64, u - 64);
+    }
+
+    for(int src = 1; src <= en; ++src) if(!vis[src])
+    {
+        ++CCs;
+        BFS(src);
+    }
+    cout << CCs << endl;
+}
+
+void MultiTest(bool Tests = 0)
+{
+    int tc = 1; (Tests) && (cin >> tc);
+    getline(cin, line); getline(cin, line);
+
+    for(int i = 1; i <= tc; ++i)
+    {
+        if(i > 1) cout << endl;
+        Solve();
+    }
+}
+
+/**------------------------->>  Main  <<-------------------------**/
+
+int main()
+{
+    Fast(); File(); MultiTest(1);
+}