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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3.  
  4. long long g[53], f[53][256];
  5. int n, m;
  6. string s;
  7.  
  8. int main()
  9. {
  10.     #define name "taoxau"
  11.     if (fopen(name".INP", "r"))
  12.     {
  13.         freopen(name".INP", "r", stdin);
  14.         freopen(name".OUT", "w", stdout);
  15.     }
  16.  
  17.     cin >> n >> m;
  18.     cin >> s;
  19.     int ns = s.size();
  20.     for (int i = 0; i < ns; i++)
  21.     {
  22.         int y = s[i];
  23.         for (int x = i + 1; x > 1; x--)
  24.         {
  25.             g[x] -= f[x][y];
  26.             f[x][y] = g[x-1];
  27.             g[x] += f[x][y];
  28.         }
  29.         if (f[1][y] == 0)
  30.         {
  31.             f[1][y]= 1;
  32.             g[1] += 1;
  33.         }
  34.     }
  35.     long long ans = 0;
  36.     for (int i = m; i <= n; i++)
  37.         ans += g[i];
  38.     cout << ans;
  39. }
  40.  
Success #stdin #stdout 0s 5292KB
comments (?)
stdin
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4 3
KHOA
stdout
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5
https://ideone.com/KKdnJZ
language:
C++14 (clang 8.0)
created:
8 days ago
visibility:
public

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