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  1. #define task "CONSTRUCT"
  2.  
  3. #include <iostream>
  4. #include <cstdio>
  5. #include <iomanip>
  6. #include <cassert>
  7.  
  8. using namespace std;
  9.  
  10. using ll = long long;
  11. using ld = long double;
  12.  
  13. constexpr int N = 1e5 + 5;
  14. int n;
  15. ll x[N], y[N];
  16. ld a[N], b[N];
  17.  
  18. void Read()
  19. {
  20.     cin >> n;
  21.  
  22.     for (int i = 1; i <= n; ++i)
  23.         cin >> x[i] >> y[i];
  24. }
  25.  
  26. ld SolveEquation(ll c1, ll c2)
  27. {
  28.     // assert(!((c1 + c2) & 1));
  29.     return (ld)1.0 * (c1 + c2) / 2;
  30. }
  31.  
  32. void Cal(ll x[N], ld a[N], int n)
  33. {
  34.     ll tmp = 0;
  35.  
  36.     for (int i = 1; i < n; ++i)
  37.         if (i & 1)
  38.             tmp = tmp + x[i] * 2;
  39.         else
  40.             tmp = tmp - x[i] * 2;
  41.  
  42.     a[1] = SolveEquation(x[n] * 2, tmp);
  43.  
  44.     for (int i = 2; i <= n; ++i)
  45.         a[i] = x[i - 1] * 2 - a[i - 1];
  46. }
  47.  
  48. void Constrain_4(ll x[N], ld a[N])
  49. {
  50.     ld I2 = (x[1] + x[2]) / 2.0,
  51.        I3 = (x[2] + x[3]) / 2.0,
  52.        I4 = (x[3] + x[4]) / 2.0,
  53.        I1 = (x[4] + x[1]) / 2.0,
  54.        I = (x[1] + x[3]) / 2.0;
  55.  
  56.     // a_1 + I = 2I1 => a_1 = 2I1 - I
  57.  
  58.     a[1] = 2 * I1 - I;
  59.     a[2] = 2 * I2 - I;
  60.     a[3] = 2 * I3 - I;
  61.     a[4] = 2 * I4 - I;
  62. }
  63.  
  64. void Solve()
  65. {
  66.     if (n == 4)
  67.     {
  68.         Constrain_4(x, a);
  69.         Constrain_4(y, b);
  70.  
  71.         for (int i = 1; i <= n; ++i)
  72.             cout << fixed << setprecision(2) << a[i] << " " << b[i] << "\n";
  73.     }
  74.     else
  75.     {
  76.         Cal(x, a, n);
  77.         Cal(y, b, n);
  78.  
  79.         for (int i = 1; i <= n; ++i)
  80.             cout << fixed << setprecision(2) << a[i] << " " << b[i] << "\n";
  81.     }
  82. }
  83.  
  84. int32_t main()
  85. {
  86.     ios::sync_with_stdio(0);
  87.     cin.tie(0);
  88.     cout.tie(0);
  89.     if (fopen(task ".INP", "r"))
  90.     {
  91.         freopen(task ".INP", "r", stdin);
  92.         freopen(task ".OUT", "w", stdout);
  93.     }
  94.  
  95.     Read();
  96.     Solve();
  97. }
  98.  
Success #stdin #stdout 0s 5932KB
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https://ideone.com/nTpYI7
language:
C++14 (gcc 8.3)
created:
10 hours ago
visibility:
public

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