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  1. /* AUTHOR: TUAN ANH - BUI */
  2. // ~~ icebear ~~
  3. #include <bits/stdc++.h>
  4. using namespace std;
  5.  
  6. typedef long long ll;
  7. typedef pair<int, int> ii;
  8. typedef pair<int, ii> iii;
  9.  
  10. template<class X, class Y>
  11.     bool minimize(X &x, const Y &y) {
  12.         if (x > y) return x = y, true;
  13.         return false;
  14.     }
  15.  
  16. template<class X, class Y>
  17.     bool maximize(X &x, const Y &y) {
  18.         if (x < y) return x = y, true;
  19.         return false;
  20.     }
  21.  
  22. #define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
  23. #define FORR(i,a,b) for(int i=(a); i>=(b); --i)
  24. #define REP(i, n) for(int i=0; i<(n); ++i)
  25. #define RED(i, n) for(int i=(n)-1; i>=0; --i)
  26. #define MASK(i) (1LL << (i))
  27. #define BIT(S, i) (((S) >> (i)) & 1)
  28. #define mp make_pair
  29. #define pb push_back
  30. #define fi first
  31. #define se second
  32. #define all(x) x.begin(), x.end()
  33. #define task "icebear"
  34. /*END OF TEMPLATE. ICEBEAR AND THE CAT WILL WIN TST26 */
  35.  
  36. const int MOD = 1e9 + 7;
  37. const int inf = (int)1e9 + 27092008;
  38. const ll INF  = (ll)1e18 + 27092008;
  39. const int N = 2e5 + 5;
  40. int numNode, limitSize;
  41. vector<int> G[N];
  42. int high[N], tour[N << 1], pos[N], minHigh[N << 1][20], timer = 0, curSize = 0;
  43. set<int> nodes;
  44.  
  45. void dfs(int u, int par) {
  46.     pos[u] = ++timer;
  47.     tour[timer] = u;
  48.     for(int v : G[u]) if (v != par) {
  49.         high[v] = high[u] + 1;
  50.         dfs(v, u);
  51.         tour[++timer] = u;
  52.     }
  53. }
  54.  
  55. #define MIN_HIGH(x, y) (high[x] < high[y] ? x : y)
  56. int LCA(int u, int v) {
  57.     int l = pos[u], r = pos[v];
  58.     if (l > r) swap(l, r);
  59.     int k = __lg(r - l + 1);
  60.     return MIN_HIGH(minHigh[l][k], minHigh[r - MASK(k) + 1][k]);
  61. }
  62.  
  63. void update(int u, int sign) {
  64.     nodes.insert(pos[u]);
  65.     auto it = nodes.find(pos[u]);
  66.     int prv = (it == nodes.begin() ? tour[*prev(nodes.end())] : tour[*prev(it)]);
  67.     int nxt = (next(it) == nodes.end() ? tour[*nodes.begin()] : tour[*next(it)]);
  68.  
  69.     curSize -= sign * (high[LCA(u, nxt)] + high[LCA(u, prv)] - high[LCA(prv, nxt)]);
  70.     curSize += sign * high[u];
  71.  
  72.     if (sign == -1) nodes.erase(it);
  73. }
  74.  
  75. void init(void) {
  76.     cin >> numNode >> limitSize;
  77.     FOR(i, 2, numNode) {
  78.         int u, v;
  79.         cin >> u >> v;
  80.         G[u].pb(v);
  81.         G[v].pb(u);
  82.     }
  83. }
  84.  
  85. void process(void) {
  86.     dfs(1, -1);
  87.     FOR(i, 1, timer) minHigh[i][0] = tour[i];
  88.     FOR(j, 1, 19) FOR(i, 1, timer - MASK(j) + 1)
  89.         minHigh[i][j] = MIN_HIGH(minHigh[i][j - 1], minHigh[i + MASK(j - 1)][j - 1]);
  90.     int l = 1, ans = 0;
  91.     FOR(r, 1, numNode) {
  92.         update(r, +1);
  93.         while(curSize >= limitSize) update(l++, -1);
  94.         maximize(ans, r - l + 1);
  95.     }
  96.     cout << ans;
  97. }
  98.  
  99. int main() {
  100.     ios_base::sync_with_stdio(0);
  101.     cin.tie(0); cout.tie(0);
  102.     if (fopen(task".inp", "r")) {
  103.         freopen(task".inp", "r", stdin);
  104.         freopen(task".out", "w", stdout);
  105.     }
  106.     int tc = 1;
  107. //    cin >> tc;
  108.     while(tc--) {
  109.         init();
  110.         process();
  111.     }
  112.     return 0;
  113. }
  114.  
  115.  
Success #stdin #stdout 0.01s 11892KB
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https://ideone.com/hOEhtd
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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