Solution: First, we can note that: when i is odd number, f(i)=2.Then we consider the case that f(i)=3. Based on the definition, if and only if i is even number and i cannot be divisible by 3, then f(i)=3.…
A. Pretty Permutations Solution: Obviously, only the two neighbors need to exchange positions with each other.For the case where n is an odd number, only the last three bits need to be exchanged with each other.…
A. Contest Start Solution: Each participant will make the following $\frac{t}{x}$ participants dissatisfied. But for last few participants, because no more participants following, so need subtract it.…
Solution: For each product, we will buy exactly $a_i$ items. We will not buy more items. So, the total number items we buy will not change (because…
A. Arithmetic Array Solution: For the sum less than n, we just need append one number to make the sum equal to n. For the sum more than n, we append some zero to make n equal to the sum.…
Solution: We can separate the number to 3 categories: odd, even but not include $2^n$ and $2^n$. Then we can get the state transition brought by one step operation:…
A. Stone Game Solution: Let us find the position of minimum and maximum value. Then there are 4 ways to remove: remove from left to right.remove from right to left.…
A. Omkar and Bad Story Solution: Obviously, if there is any number in the array is less than zero. Then by using this number as the subtracted number, the array can grow indefinitely.…
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