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  1. #include "bits/stdc++.h"
  2.  
  3. #define clr(x) memset((x), 0, sizeof(x))
  4. #define all(x) (x).begin(), (x).end()
  5. #define pb push_back
  6. #define mp make_pair
  7. #define in(x) int (x); input((x));
  8. #define x first
  9. #define y second
  10. typedef int itn;
  11.  
  12. #define next next12345
  13. #define prev prev12345
  14. #define left lefdsf232
  15. #define right rig43783
  16. #define x1 x12345
  17. #define y1 y12345
  18.  
  19. using namespace std;
  20.  
  21. template<typename T>
  22. T gcd(T x, T y) {
  23.     while (y > 0) {
  24.         x %= y;
  25.         swap(x, y);
  26.     }
  27.     return x;
  28. }
  29.  
  30. template<class _T>
  31. inline _T sqr(const _T &x) {
  32.     return x * x;
  33. }
  34.  
  35. template<class _T>
  36. inline string tostr(const _T &a) {
  37.     ostringstream os("");
  38.     os << a;
  39.     return os.str();
  40. }
  41.  
  42. typedef long double ld;
  43. typedef long long ll;
  44. typedef unsigned long long ull;
  45. typedef pair<int, int> PII;
  46. const long double PI = 3.1415926535897932384626433832795L;
  47.  
  48. template<typename T>
  49. inline void input(T &a) {
  50.     static int c;
  51.     a = 0;
  52.     while (!isdigit(c = getchar()) && c != '-') {}
  53.     char neg = 0;
  54.     if (c == '-') {
  55.         neg = 1;
  56.         c = getchar();
  57.     }
  58.     while (isdigit(c)) {
  59.         a = 10 * a + c - '0';
  60.         c = getchar();
  61.     }
  62.     if (neg) a = -a;
  63. }
  64.  
  65. template<typename T = int>
  66. inline T nxt() {
  67.     T res;
  68.     input(res);
  69.     return res;
  70. }
  71.  
  72. const int N = 30000;
  73.  
  74. struct dsu {
  75.     int p[N];
  76.     int sz[N];
  77.     int cnt;
  78.  
  79.     void init(int n) {
  80.         for (int i = 0; i < n; ++i) {
  81.             p[i] = i;
  82.             sz[i] = 1;
  83.         }
  84.         cnt = n;
  85.     }
  86.  
  87.     inline int get(int v) {
  88.         if (p[v] != v) {
  89.             p[v] = get(p[v]);
  90.         }
  91.         return p[v];
  92.     }
  93.  
  94.     inline void unite(int a, int b) {
  95.         a = get(a);
  96.         b = get(b);
  97.         if (a == b) {
  98.             return;
  99.         }
  100.         --cnt;
  101.         if (sz[a] > sz[b]) {
  102.             swap(a, b);
  103.         }
  104.         p[a] = b;
  105.         sz[b] += sz[a];
  106.     }
  107. };
  108.  
  109. const int K = 17;
  110.  
  111. vector <dsu> x[K];
  112.  
  113. struct edge {
  114.     int from;
  115.     int to;
  116.     int len;
  117.     int id;
  118.     bool operator<(const edge & e) const {
  119.         return len < e.len;
  120.     }
  121. };
  122.  
  123. int k;
  124.  
  125.  
  126. edge e[N];
  127.  
  128. dsu empty;
  129.  
  130. dsu W;
  131.  
  132. int vertices[N + N + N + N];
  133.  
  134. int check(int l, int r) {
  135.     int p1 = (l + k - 1) / k;
  136.     int p2 = (r + 1) / k;
  137.  
  138.     int X = p1 * k;
  139.     int Y = p2 * k;
  140.  
  141.     p2 -= p1 + 1;
  142.  
  143.     int sz = 0;
  144.  
  145.     if (p2 < 0) {
  146.         for (int x = l; x <= r; ++x) {
  147.             int A = e[x].from;
  148.             int B = e[x].to;
  149.             if (A != B) {
  150.                 vertices[sz++] = A;
  151.                 vertices[sz++] = B;
  152.             }
  153.         }
  154.  
  155.         W.cnt = empty.cnt;
  156.         for (int i = 0; i < sz; ++i) {
  157.             W.p[vertices[i]] = vertices[i];
  158.             W.sz[vertices[i]] = 1;
  159.         }
  160.  
  161.         for (int x = l; x <= r; ++x) {
  162.             int A = e[x].from;
  163.             int B = e[x].to;
  164.             if (A != B) W.unite(A, B);
  165.         }
  166.     } else {
  167.         dsu & v = x[p1][p2];
  168.  
  169.         for (int x = l; x < X; ++x) {
  170.             int A = v.get(e[x].from);
  171.             int B = v.get(e[x].to);
  172.             if (A != B) {
  173.                 vertices[sz++] = A;
  174.                 vertices[sz++] = B;
  175.             }
  176.         }
  177.  
  178.         for (int x = Y; x <= r; ++x) {
  179.             int A = v.get(e[x].from);
  180.             int B = v.get(e[x].to);
  181.             if (A != B) {
  182.                 vertices[sz++] = A;
  183.                 vertices[sz++] = B;
  184.             }
  185.         }
  186.  
  187.         W.cnt = v.cnt;
  188.         for (int i = 0; i < sz; ++i) {
  189.             W.p[vertices[i]] = vertices[i];
  190.             W.sz[vertices[i]] = 1;
  191.         }
  192.  
  193.         for (int i = 0; i < sz; i += 2) {
  194.             W.unite(vertices[i], vertices[i + 1]);
  195.         }
  196.     }
  197.  
  198.     return W.cnt == 1;
  199. }
  200.  
  201. int main() {
  202.     //#define int long
  203. #ifdef LOCAL
  204.     freopen("input.txt", "r", stdin);
  205.     //freopen("output.txt", "w", stdout);
  206. #else
  207. #define fname "onearmedbandit"
  208.     //freopen(fname".in", "r", stdin);
  209.     //freopen(fname".out", "w", stdout);
  210. #endif
  211.  
  212.     int n = nxt(), m = nxt();
  213.  
  214.     for (int i = 0; i < m; ++i) {
  215.         e[i].from = nxt() - 1;
  216.         e[i].to = nxt() - 1;
  217.         e[i].len = nxt();
  218.         e[i].id = i;
  219.     }
  220.  
  221.  
  222.     empty.init(n);
  223.  
  224.     sort(e, e + m);
  225.  
  226.     k = (m + K - 1) / K;
  227.  
  228.  
  229.  
  230.     for (int i = 0, t = 0; i < m; i += k, ++t) {
  231.         for (int j = i; j < m; ++j) {
  232.             if (j % k == 0) {
  233.                 if (j == i) {
  234.                     x[t].push_back(dsu());
  235.                     x[t].back().init(n);
  236.                 } else {
  237.                     x[t].push_back(dsu());
  238.                     dsu & last = x[t][x[t].size() - 2];
  239.                     dsu & cur = x[t].back();
  240.  
  241.                     memcpy(cur.p, last.p, sizeof(int) * n);
  242.                     memcpy(cur.sz, last.sz, sizeof(int) * n);
  243.                     cur.cnt = last.cnt;
  244.                 }
  245.             }
  246.             x[t].back().unite(e[j].from, e[j].to);
  247.         }
  248.     }
  249.  
  250.  
  251.     //cout << check(0, m - 1) << endl;
  252.  
  253.     //return 0;
  254.  
  255.  
  256.     int r = 0;
  257.  
  258.     int best = INT_MAX;
  259.  
  260.     int L = 0, R = m - 1;
  261.  
  262.     for (int i = 0; i < m; ++i) {
  263.         r = max(r, i + n - 2);
  264.         while (r < m && !check(i, r)) {
  265.             ++r;
  266.         }
  267.         if (r < m) {
  268.             int v = e[r].len - e[i].len;
  269.             if (v < best) {
  270.                 best = v;
  271.                 L = i, R = r;
  272.             }
  273.         } else {
  274.             break;
  275.         }
  276.     }
  277.  
  278.     vector <int> ans;
  279.  
  280.     empty.init(n);
  281.  
  282.     for (int x = L; x <= R; ++x) {
  283.         int A = empty.get(e[x].from);
  284.         int B = empty.get(e[x].to);
  285.         if (A != B) {
  286.             ans.push_back(e[x].id);
  287.             empty.unite(A, B);
  288.         }
  289.     }
  290.  
  291. //    long long mem = 0;
  292. //    for (int i = 0; i < K; ++i) {
  293. //        for (const auto & X : x[i]) {
  294. //            mem += sizeof(X);
  295. //        }
  296. //    }
  297. //
  298. //    cerr << mem << endl;
  299.  
  300.     //cout << ans.size() << endl;
  301.     assert(ans.size() == n - 1);
  302.  
  303.     sort(all(ans));
  304.  
  305.     for (int x : ans) {
  306.         cout << x + 1 << " ";
  307.     }
  308.  
  309.     cout << "\n";
  310.  
  311. #ifdef LOCAL
  312.     cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC * 1000 << " ms." << endl;
  313. #endif
  314.     return 0;
  315. }
Time limit exceeded #stdin #stdout 5s 4668KB
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https://ideone.com/tsRwCs
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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