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  1. // Author: 4uckd3v - Nguyen Cao Duc
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4.  
  5. typedef long long ll;
  6.  
  7. const int MAX_N = 1e3;
  8. const int MOD = 1e9 + 7;
  9. const string br = "([{)}]";
  10. const ll INF = 2e18;
  11.  
  12. int n, k;
  13. ll kth;
  14. string st;
  15. ll dp[MAX_N + 5][MAX_N + 5][2];
  16.  
  17. bool open(char c) {
  18.     return c == '(' || c == '[' || c == '{';
  19. };
  20.  
  21. bool matchBracket(char o, char c) {
  22.     return (o == '(' && c == ')') || (o == '[' && c == ']') || (o == '{' && c == '}');
  23. };
  24.  
  25. ll DP(int idx, int diff, bool ok) {
  26.     if (idx > n) return (diff == 0 && ok);
  27.     if (dp[idx][diff][ok] != -1) return dp[idx][diff][ok];
  28.  
  29.     ll &ret = dp[idx][diff][ok] = 0;
  30.     if (diff > 0) ret += DP(idx + 1, diff - 1, ok);
  31.     if (diff < k) ret += DP(idx + 1, diff + 1, ok || (diff + 1) == k) * 3;
  32.  
  33.     ret = min(ret, INF);
  34.  
  35.     return ret;
  36. };
  37.  
  38. ll getRank(const string &st) {
  39.     int diff = 0;
  40.     bool ok = false;
  41.     ll rank = 1;
  42.  
  43.     stack<char> match;
  44.     for (int i = 1; i <= n; i++) {
  45.         for (char ch : br) {
  46.             if (ch == st[i]) break;
  47.             if (diff < k && open(ch)) rank += DP(i + 1, diff + 1, ok || (diff + 1) == k);
  48.             if (diff > 0 && !open(ch)) {
  49.                 if (!match.empty() && matchBracket(match.top(), ch))
  50.                     rank += DP(i + 1, diff - 1, ok);
  51.             }
  52.         };
  53.  
  54.         if (open(st[i])) {
  55.             match.push(st[i]);
  56.             diff++;
  57.             ok |= diff == k;
  58.         } else {
  59.             match.pop();
  60.             diff--;
  61.         };
  62.     };
  63.  
  64.     return rank;
  65. };
  66.  
  67. string getKth(ll kth) {
  68.     int diff = 0;
  69.     bool ok = false;
  70.     string ret;
  71.     stack<char> match;
  72.  
  73.     for (int i = 1; i <= n; i++) {
  74.         ll cur = 0;
  75.         for (char ch : br) {
  76.             if (diff < k && open(ch)) {
  77.                 if (cur + DP(i + 1, diff + 1, ok || (diff + 1) == k) >= kth) {
  78.                     ret += ch;
  79.                     kth -= cur;
  80.                     diff++;
  81.                     ok |= diff == k;
  82.                     match.push(ch);
  83.                     break;
  84.                 } else
  85.                     cur += DP(i + 1, diff + 1, ok || (diff + 1) == k);
  86.             };
  87.             if (diff > 0 && !open(ch) && !match.empty() && matchBracket(match.top(), ch)) {
  88.                 if (cur + DP(i + 1, diff - 1, ok) >= kth) {
  89.                     ret += ch;
  90.                     kth -= cur;
  91.                     diff--;
  92.                     match.pop();
  93.                     break;
  94.                 } else
  95.                     cur += DP(i + 1, diff - 1, ok);
  96.             };
  97.         };
  98.     };
  99.  
  100.     return ret;
  101. };
  102.  
  103. int main() {
  104.     ios_base::sync_with_stdio(0);
  105.     cin.tie(0);
  106.     if (fopen("BRCNT1.INP", "r")) {
  107.         freopen("BRCNT1.INP", "r", stdin);
  108.         freopen("BRCNT1.OUT", "w", stdout);
  109.     };
  110.  
  111.     cin >> n >> k >> st >> kth;
  112.     st = " " + st;
  113.  
  114.     memset(dp, -1, sizeof dp);
  115.  
  116.     DP(1, 0, 0);
  117.     cout << getRank(st) << '\n';
  118.     cout << getKth(kth) << '\n';
  119. };
Success #stdin #stdout 0.01s 19404KB
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stdin 
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1
https://ideone.com/kEQMmc
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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