There are N=2^n bags of rice looking alike, N-1 of which have equal weight and one is slightly heavier. The weighing balance is of unlimited capacity. Using the balance, the minimum number of weighing required to identify the heavier bag is?
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I think it only takes 5 weighings when N=128. Am I incorrect?
agree 5 weighing for N=128 (worst case scenario you reduce to 43 15 5 2 1 after each consecutive weighing)
the last test case provided by the author is wrong: should be 5 since log(128)/log(3) < 5.
The problem is that the author do not specify an strategy. And as mentioned, dividing by 3 yields a better strategy than 6 weightings for 128. But, my guess is that the author counted the number of divisions instead of the number of weightings 128->[42 42 43] -> [14 14 14; 14 14 15]->[5 5 4; 5 5 5]->[2 2 0; 2 2 1]->[1;2]->1.