摘要：
Let's call an array A a mountain if the following properties hold: A.length >= 3 There exists some 0 < i < A.length - 1 such that A[0] < A[1] < ... A[ 阅读全文
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Let f(x) be the number of zeroes at the end of x!. (Recall that x! = 1 * 2 * 3 * ... * x, and by convention, 0! = 1.) For example, f(3) = 0 because 3! 阅读全文
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A sorted list A contains 1, plus some number of primes. Then, for every p < q in the list, we consider the fraction p/q. What is the K-th smallest fra 阅读全文
摘要：
On an N x N grid, each square grid[i][j] represents the elevation at that point (i,j). Now rain starts to fall. At time t, the depth of the water ever 阅读全文