# Connected Components in a Graph

Apr 30th, 2021
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1. #include <bits/stdc++.h>
2. #define Niloy
3. #define int int64_t
4. #define mx (int) 1e6 + 123
5. #define MOD 1e9
6. #define pb push_back
7. #define pairs pair<int, int>
8. #define vi vector<int>
9. #define vb vector<bool>
10. #define vii vector<pairs>
11. #define lb lower_bound
12. #define ub upper_bound
13. #define endl '\n'
14. #define llu unsigned long long
15. using namespace std;
16. /* ----------------------------------------------------------------------------------- */
17.
18. // Input/Output
19. #define fastInput ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
20. #define all(x) x.begin(), x.end()
21. #define square(a) (a * a)
22. #define mem(a, b) memset(a, b, sizeof(a))
23.
24. // Fractional Number
25. #define fraction()        cout.unsetf(ios::floatfield); cout.precision(10); cout.setf(ios::fixed, ios::floatfield);
26.
27. #define scan(a)           scanf("%lld", &a);
28. #define scan2(a, b)       scanf("%lld %lld", &a, &b);
29. #define scan3(a, b, c)    scanf("%lld %lld %lld", &a, &b, &c);
30. #define scan4(a, b, c, d) scanf("%lld %lld %lld %lld", &a, &b, &c, &d);
31.
32. #define scanD(a)          scanf("%lf", &a);
33. #define scanD2(a, b)      scanf("%lf %lf", &a, &b);
34. #define scanD3(a, b, c)   scanf("%lf %lf %lf", &a, &b, &c);
35. #define scanD4(a, b, c, d)scanf("%lf %lf %lf %lf", &a, &b, &c, &d);
36.
37.
38. #define print(a)           printf("%lld\n", a);
39. #define print2(a, b)       printf("%lld %lld\n", a, b);
40. #define print3(a, b, c)    printf("%lld %lld %lld\n", a, b, c);
41. #define print4(a, b, c, d) printf("%lld %lld %lld %lld\n", a, b, c, d);
42.
43. #define printD(a)          printf("%lf\n", a);
44. #define printD2(a, b)      printf("%lf %lf\n", a, b);
45. #define printD3(a, b, c)   printf("%lf %lf %lf\n", a, b, c);
46. #define printD4(a, b, c, d)printf("%lf %lf %lf %lf\n", a, b, c, d);
47. #define printTwoD(a)       printf("%.2lf\n", a);
48.
49. // File I/O
50. #define read(x)  freopen(x, "r", stdin);
51. #define write(x) freopen(x, "w", stdout);
52.
53. // Loops
54. #define rep(i, a, n) for (int i = a; i < n; i++)
55. #define REP(i, a, n) for (int i = a; i <= n; i++)
56. #define rev(i, n, a) for (int i = n - 1; i >= a; i--)
57. #define REV(i, n, a) for (int i = n; i >= a; i--)
58. #define inputArray(a,n) rep(i, 0, n) cin >> a[i];
59. #define copyArray(a,temp,n) rep(i, 0, n) temp[i]=a[i];
60. #define printArray(a,n) rep(i, 0, n) cout << a[i] << " "; cout << endl;
61.
62. /* ----------------------------------------------------------------------------------- */
63.
64. #define Cases  cout << "Case " << ++Case << ": ";
65. #define __test int tt; int Case=0; cin >> tt; while(tt--)
66. #define showTime cerr << "time = " << (clock() / CLOCKS_PER_SEC) << " sec" << '\n';
67.
68. #define dbgA2(A, n, m) {cout<<"--> "<<#A<<" = \n";rep(i, 0, n){rep(j, 0, m){cout<<A[i][j]<<"";}cout<<"\n";}cout<<"\n";}
69. #define dbgA(A, n) {cout<<" --> "<<#A<<" = (";rep(i, 0, n)cout<<A[i]<<" ";cout<<")\n";}
70. #define dbg(args...) {string sss(#args);sss+=',';cout<<" --> ";debugger::call(all(sss), args);cout<<"\n";}
71.
72. /* ----------------------------------------------------------------------------------- */
73.
74. int gcd(int n, int m) { return m ? gcd(m, n % m) : n; }
75. int lcm(int n, int m) { return n / gcd(n, m) * m; }
76.
77. struct debugger {
78.     typedef string::iterator si;
79.     static void call(si it, si ed) {}
80.     template<typename T, typename ... aT>
81.     static void call(si it, si ed, T a, aT... rest) {
82.         string b;
83.         for(; *it!=','; ++it)
84.             if(*it!=' ')
85.                 b+=*it;
86.         cout << b << "=" << a << " ";
87.         call(++it, ed, rest...);
88.     }
89. };
90.
91. /* ----------------------------------------------------------------------------------- */
92. void input() {
93. #ifdef Niloy
95.     write("output.txt");
96. #endif
97. }
98.
99. /* ----------------------------------------------------------------------------------- */
100.
101. bool vis[mx];
103.
104. void dfs(int u) {
105.     vis[u] = 1;
106.
107.     for (auto v : adj[u]) {
108.         if (!vis[v]) {
109.             dfs(v);
110.         }
111.     }
112. }
113.
114. void solve() {
115.     int n, e;
116.     scan2(n, e);
117.     rep(i, 0, e) {
118.         int u, v;
119.         scan2(u, v);
122.     }
123.     int cnt = 0;
124.     REP(i, 1, n) {
125.         if (!vis[i]) {
126.             cnt++;
127.             dfs(i);
128.         }
129.     }
130.     cout << cnt << endl;
131. }
132.
133. int32_t main() {
134.     // input();
135.     // fastInput;
136.     solve();
137.
138.     // __test {
139.     //  solve();
140.     // }
141.
142.     // showTime;
143.     return 0;
144. }
145.
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