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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. // max independent set on path [l, r]
  5. long long getMax(const vector<long long>& a, int l, int r) {
  6.     if (l > r) return 0;
  7.  
  8.     long long prev2 = 0, prev = 0;
  9.     for (int i = l; i <= r; i++) {
  10.         long long take = prev2 + a[i]; // can't use adjacent
  11.         long long skip = prev;
  12.         long long cur = max(take, skip);
  13.         prev2 = prev;
  14.         prev = cur;
  15.     }
  16.     return prev;
  17. }
  18.  
  19. int main() {
  20.     ios::sync_with_stdio(false);
  21.     cin.tie(nullptr);
  22.  
  23.     int n;
  24.     cin >> n;
  25.  
  26.     vector<long long> a(n + 1);
  27.     long long sum = 0;
  28.     for (int i = 1; i <= n; i++) {
  29.         cin >> a[i];
  30.         sum += a[i];
  31.     }
  32.  
  33.     // min edge cover = sum - max independent set
  34.     // for cycle: either skip first edge or take it
  35.     long long skip1 = getMax(a, 2, n);
  36.     long long take1 = a[1] + getMax(a, 3, n - 1);
  37.     long long maxIS = max(skip1, take1);
  38.  
  39.     cout << sum - maxIS << "\n";
  40.     return 0;
  41. }
Success #stdin #stdout 0.01s 5308KB
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https://ideone.com/NLwMBB
language:
C++14 (gcc 8.3)
created:
12 hours ago
visibility:
public

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