Given an integer n, denoting the number of cuts that can be made on a pancake, find the maximum number of pieces that can be formed by making n cuts.
Input : n = 1 Output : 2 With 1 cut we can divide the pancake in 2 pieces Input : 2 Output : 4 With 2 cuts we can divide the pancake in 4 pieces Input : 3 Output : 7 We can divide the pancake in 7 parts with 3 cuts Input : 50 Output : 1276
Let f(n) denote the maximum number of pieces that can be obtained by making n cuts. Trivially, f(0) = 1 As there'd be only 1 piece without any cut. Similarly, f(1) = 2 Proceeding in similar fashion we can deduce the recursive nature of the function. The function can be represented recursively as : f(n) = n + f(n-1) Hence a simple solution based on the above formula can run in O(n).
We can optimize above formula.
We now know , f(n) = n + f(n-1) Expanding f(n-1) and so on we have , f(n) = n + n-1 + n-2 + ...... + 1 + f(0) which gives, f(n) = (n*(n+1))/2 + 1
Hence with this optimization, we can answer all the queries in O(1).
Below is the implementation of above idea :
2 4 7 1276
References : oeis.org
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