Problem Description: Given N, M, find the last non-zero digit in N! / (N - M)!.Constraints: 0 ≤ M ≤ N ≤ 2e7Solution: We can find a and k such that in O(lg x) time, given that e is 2 or 5 (because they are prime, we can apply Wilson's theor…

1006 -- Biorhythms題意： 細節不好說明，但總之給 p, i, e, d，滿足聯立模方程式： ( x + d ) % 23 = p ( x + d ) % 28 = e ( x + d ) % 33 = i 求 x。解法： 就是一個中國剩餘定理模板。28 非質數，如果要用尤拉定理搞要先求 phi 函數才能求模逆元，但最近…