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  1. #include<bits/stdc++.h>
  2. #define M 2004
  3. using namespace std;
  4.  
  5. string a, b;
  6. int dp[M][M];
  7.  
  8. int main()
  9. {
  10.     ios_base::sync_with_stdio(0);
  11.     cin.tie(0);     cout.tie(0);
  12.  
  13.     cin >> a;
  14.     b = a;
  15.     reverse(b.begin(), b.end());
  16.     int n = a.size();
  17.     a = ' ' + a;
  18.     b = ' ' + b;
  19.     for(int i = 1; i <= n; i++)
  20.     {
  21.         for(int j = 1; j <= n; j++)
  22.         {
  23.             if(a[i] == b[j])   dp[i][j] = dp[i - 1][j - 1] + 1;
  24.             else    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
  25.         }
  26.     }
  27.     string ans = "";
  28.     int x = dp[n][n];
  29.     int m = n;
  30.     while(1)
  31.     {
  32.         if(a[n] == b[m])
  33.         {
  34.             ans += a[n];
  35.             n--;
  36.             m--;
  37.         }
  38.         else
  39.         {
  40.             if(dp[n][m] == dp[n - 1][m])  n--;
  41.             else    m--;
  42.         }
  43.         if(ans.size() == x)  break;
  44.     }
  45.     cout << ans;
  46. }
  47.  
Success #stdin #stdout 0s 5288KB
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level
https://ideone.com/O9tnZP
language:
C++14 (clang 8.0)
created:
11 days ago
visibility:
public

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