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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. const long long oo = 1e18 + 7;
  4. int n;
  5. long long sum;
  6. int a[5005];
  7. long long dp[5005][5005];
  8.  
  9. long long solve(int l, int r) {
  10.     if (l > r) return 0;
  11.     if (dp[l][r] != -oo) return dp[l][r];
  12.     int res = l - 1 + n - r;
  13.     long long cur;
  14.     if (res % 2 == 0) {
  15.         cur = -oo;
  16.         cur = max(cur, solve(l + 1, r) + a[l]);
  17.         cur = max(cur, solve(l, r - 1) + a[r]);
  18.     } else {
  19.         cur = oo;
  20.         cur = min(cur, solve(l + 1, r) - a[l]);
  21.         cur = min(cur, solve(l, r - 1) - a[r]);
  22.     }
  23.     return dp[l][r] = cur;
  24. }
  25.  
  26. main() {
  27.     ios_base::sync_with_stdio(false);
  28.     cin.tie(0); cout.tie(0);
  29.     freopen("TEST.inp", "r", stdin);
  30.     freopen("TEST.out", "w", stdout);
  31.     cin >> n;
  32.     for (int i = 1; i <= n; i++) {
  33.         cin >> a[i];
  34.         sum += a[i];
  35.     }
  36.  
  37.     for (int i = 1; i <= n; i++)
  38.     for (int j = 1; j <= n; j++) dp[i][j] = -oo;
  39.     long long ans = solve(1, n);
  40.  
  41.     cout << (sum + ans) / 2 << '\n';
  42.  
  43.     return 0;
  44. }
  45.  
Success #stdin #stdout 0s 5324KB
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https://ideone.com/sX5S3j
language:
C++14 (gcc 8.3)
created:
7 hours ago
visibility:
public

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