441_ Arranging_Coins

旧城等待， 2022-06-08 00:51 269阅读 0赞 
  1. /*
  2. 441. Arranging Coins
  4. You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins.
  6. Given n, find the total number of full staircase rows that can be formed.
  8. n is a non-negative integer and fits within the range of a 32-bit signed integer.
  10. Example 1:
  12. n = 5
  14. The coins can form the following rows:
  15. ¤
  16. ¤ ¤
  17. ¤ ¤
  19. Because the 3rd row is incomplete, we return 2.
  20. */
  21. //思路，就像高斯定理一样，首项加末项乘香树除以2就是n
  22. //解法一  83%  23ms
  23. int arrangeCoins(int n) {
  24.     long long int i = n;
  25.     i = (sqrt(8*i+1)-1)/2;
  26.     return i;
  27. }
  28. /解法二   98%  19ms
  29. //我试着把long long int 改成float，但是2146467959数据没法通过， 超出了范围，如果改成double就可以了。直接怼到98.65%
  30. int arrangeCoins(int n) {
  31.     double i = n;
  32.     i = (sqrt(8*i+1)-1)*0.5;
  33.     return i;
  34. }

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