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  1. // Author: Ivan Kazmenko (gassa@mail.ru)
  2. module solution;
  3. // version = IO_FILES;
  4. import std.algorithm;
  5. import std.range;
  6. import std.stdio;
  7. import std.typecons;
  8.  
  9. immutable string PROBLEM_NAME = "lights";
  10.  
  11. alias Lamp = Tuple !(int, q{x}, int, q{r});
  12.  
  13. bool check (Lamp [] lamps)
  14. {
  15. 	int limit = lamps.front.x;
  16. 	foreach (ref lamp; lamps)
  17. 	{
  18. 		if (lamp.x > limit)
  19. 		{
  20. 			return false;
  21. 		}
  22. 		limit = max (limit, lamp.x + lamp.r);
  23. 	}
  24. 	return true;
  25. }
  26.  
  27. void main ()
  28. {
  29. 	version (IO_FILES)
  30. 	{
  31. 		stdin  = File (PROBLEM_NAME ~ ".in",  "rt");
  32. 		stdout = File (PROBLEM_NAME ~ ".out", "wt");
  33. 	}
  34.  
  35. 	int n;
  36. 	while (readf (" %s", &n) > 0)
  37. 	{
  38. 		auto lamps = new Lamp [n];
  39. 		foreach (ref lamp; lamps)
  40. 		{
  41. 			readf (" %s %s", &lamp.x, &lamp.r);
  42. 		}
  43. 		auto lampsRev = lamps.retro
  44. 		    .map !(lamp => Lamp (-lamp.x, lamp.r)).array;
  45. 		writeln (check (lamps) && check (lampsRev) ?
  46. 		    (lamps.back.x - lamps.front.x) * 3L : -1);
  47. 	}
  48. }
  49.  
Success #stdin #stdout 0s 17424KB
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5
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stdout
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21
https://ideone.com/IhGow3
language:
D (dmd 2.085.0)
created:
7 years ago
visibility:
secret

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