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El_GEMMY

wavio sequence (binary search)

Jun 4th, 2022
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C++ 3.96 KB | None | 0 0
  1. // Those who cannot remember the past are
  2. // condemned to repeat it (use DP -_-)
  3. // - George Santayana
  4.  
  5. #include <bits/stdc++.h>
  6. #include <ext/pb_ds/assoc_container.hpp>
  7. #include <ext/pb_ds/tree_policy.hpp>
  8.  
  9. using namespace std;
  10. using namespace __gnu_pbds;
  11.  
  12. #define all(v) v.begin(), v.end()
  13. #define rall(v) v.rbegin(), v.rend()
  14. #define ll long long
  15. #define ull unsigned long long
  16. #define MOD 1000000007
  17. #define PI 3.14159265
  18. #define ceil(a, b) (((a) / (b)) + ((a) % (b) ? 1 : 0))
  19. #define imin INT_MIN
  20. #define imax INT_MAX
  21. #define llmax LLONG_MAX
  22. #define llmin LLONG_MIN
  23. #define inf 2000000000
  24. #define nl '\n'
  25. #define ppcnt __builtin_popcount
  26. #define ppcntll __builtin_popcountll
  27. #define clz __builtin_clz
  28. #define clzll __builtin_clzll
  29. #define ctz __builtin_ctz
  30. #define ctzll __builtin_ctzll
  31. #define modulo(a, b, mod) ((((a) % (mod)) + ((b) % (mod))) % (mod))
  32. #define cnte(v, x) count(all(v), (x))
  33. #define mine(v) min_element(all(v))
  34. #define maxe(v) max_element(all(v))
  35. #define updmin(a, b) a = min(a, b)
  36. #define updmax(a, b) a = max(a, b)
  37. #define findmod(x, m) x = ((x) % (m) + (m)) % m
  38. #define getmod(x, m) ((x) % (m) + (m)) % (m)
  39. #define debug(x) cout << "x: " << (x) << nl;
  40. #define debug2(x, y) cout << "x: " << (x) << " y: " << y << nl;
  41. #define ordered_set tree<int, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>
  42. #define ordered_map tree<int, int, less<>, rb_tree_tag, tree_order_statistics_node_update>
  43.  
  44. //vector<int> dx = {0, 0, 1, -1, 1, 1, -1, -1}, dy = {1, -1, 0, 0, 1, -1, 1, -1};
  45. //vector<int> dx = {0, 0, 1, -1}, dy = {1, -1, 0, 0};
  46.  
  47. template<typename T = int> istream& operator>>(istream& in, vector<pair<int, int>>& v){
  48.     for (auto& [x, y] : v) in >> x >> y;
  49.     return in;
  50. }
  51.  
  52. template<typename T = int> istream& operator>>(istream& in, vector<T>& v){
  53.     for (T& i : v) in >> i;
  54.     return in;
  55. }
  56.  
  57. template<typename T = int> ostream& operator<<(ostream& out, const vector<T>& v){
  58.     for (const T& x : v)
  59.         out << x << ' ';
  60.     return out;
  61. }
  62.  
  63. template<typename T = pair<int, int>> ostream& operator << (ostream& out, const vector<pair<int, int>>& v){
  64.     for(auto& [x, y] : v){
  65.         out << x << ' ' << y << nl;
  66.     }
  67.     return out;
  68. }
  69.  
  70. void Start_Crushing() {
  71.     ios_base::sync_with_stdio(false);
  72.     cin.tie(nullptr);
  73.     cout.tie(nullptr);
  74. #ifndef ONLINE_JUDGE
  75.     freopen("input.txt", "r", stdin);
  76.     freopen("output.txt", "w", stdout);
  77. #endif
  78. }
  79.  
  80. void solve(){
  81.     int n;
  82.     while(cin >> n){
  83.         vector<int> v(n);
  84.         cin >> v;
  85.  
  86.  
  87.         vector<int> lis(n, 1), lds(n, 1);
  88.  
  89.         vector<int> d(n + 1, inf);
  90.         d.front() = -inf;
  91.  
  92.         for (int i = 0; i < n; i++) {
  93.             int pos = int(upper_bound(all(d), v[i]) - d.begin());
  94.             bool found = d[int(lower_bound(all(d), v[i]) - d.begin())] == v[i];
  95.  
  96.             if (d[pos - 1] < v[i] and v[i] < d[pos]) {
  97.                 d[pos] = v[i];
  98.             }
  99.             lis[i] = pos - found;
  100.         }
  101.  
  102.         d.assign(n + 1, inf);
  103.         d.front() = -inf;
  104.  
  105.         reverse(all(v));
  106.  
  107.         for (int i = 0; i < n; i++) {
  108.             int pos = int(upper_bound(all(d), v[i]) - d.begin());
  109.             bool found = d[int(lower_bound(all(d), v[i]) - d.begin())] == v[i];
  110.  
  111.             if (d[pos - 1] < v[i] and v[i] < d[pos]) {
  112.                 d[pos] = v[i];
  113.             }
  114.             lds[n - i - 1] = pos - found;
  115.         }
  116.  
  117.         int ans = 0;
  118.         for (int i = 0; i < n; i++) {
  119.             updmax(ans, min(lis[i], lds[i]) * 2 - 1);
  120.         }
  121.         cout << ans << nl;
  122.     }
  123. }
  124.  
  125. int main(){
  126.     Start_Crushing();
  127. //    freopen("perm.in", "r", stdin);
  128.  
  129.     int t = 1;
  130. //    /*Multiple test cases?*/ cin >> t;
  131.     while (t--) {
  132.         solve();
  133. //        if(!t)
  134. //            break;
  135. //        cout << nl;
  136.     }
  137.  
  138. //    for(int tc = 1; tc <= t; tc++){
  139. //        cout << "Case #" << tc << ": ";
  140. //        solve();
  141. //        if(tc != t)
  142. //            cout << nl;
  143. //    }
  144.  
  145.     return 0;
  146. }
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