Unlimited_Time's blog

By Unlimited_Time, 6 months ago, In English,

99A - Помогите Тридевятому царству

Using C++, there is a simple manner to implement string parsing. For this problem, we can replace '.' with space, and initialize an 'istringstream' type with this modified string. Then, we define two string variables, and initialize them with 'istringstream' as a standard input. The next work is to find the last digit of the first string and the first digit of the second string, and output the answer according to the requirement.

99B - Помогите Повару Герасиму

Take care of two special cases n = 1, 2. For n ≥ 3, we can find out the maximum and minimum values, denoted as min and max, respectively. Besides, we should find out all the other values that are neither min nor max. If such value is unique, and equal to , the current configuration can be recovered.

99C - Помогите Василисе Премудрой

The complete permutation has 6! = 720 patterns. Therefore, we can compare every one with all the other ones to check whether it results in a unique pattern or not. Now we should figure out how to determine that two patterns are equivalent after some rotation.

As an efficient manner, we can mark the six planes with front, back, up, down, left and right. Then, we fix one plane as the top, and rotate 0, 90, 180, 270 degrees to obtain four equivalent patterns. As there are 6 planes to serve as the top, the total number of equivalent patterns are 6 × 4 = 24.

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