ACM程序设计02.pptVIP

ACM程序设计 第二讲 枚举法 又称穷举法 从可能的解的集合中一一枚举各元素，用给定的检验条件判定哪些是无用的，哪些是有用的。能使命题成立，就是问题的解。 枚举法本质上是有哪些信誉好的足球投注网站算法，但与有哪些信誉好的足球投注网站有所不同，适用于枚举法的问题必须满足两个条件： 1 可预先确定解的个数 2 解变量A1，A2，。。。，An的值的可能变化范围预先确定 例题 Safecraker ZOJ1403 === Op tech briefing, 2002/11/02 06:42 CST === The item is locked in a Klein safe behind a painting in the second-floor library. Klein safes are extremely rare; most of them, along with Klein and his factory, were destroyed in World War II. Fortunately old Brumbaugh from research knew Kleins secrets and wrote them down before he died. A Klein safe has two distinguishing features: a combination lock that uses letters instead of numbers, and an engraved quotation on the door. A Klein quotation always contains between five and twelve distinct uppercase letters, usually at the beginning of sentences, and mentions one or more numbers. Five of the uppercase letters form the combination that opens the safe. By combining the digits from all the numbers in the appropriate way you get a numeric target. (The details of constructing the target number are classified.) To find the combination you must select five letters v, w, x, y, and z that satisfy the following equation, where each letter is replaced by its ordinal position in the alphabet (A=1, B=2, ..., Z=26). The combination is then vwxyz. If there is more than one solution then the combination is the one that is lexicographically greatest, i.e., the one that would appear last in a dictionary. v - w^2 + x^3 - y^4 + z^5 = target For example, given target 1 and letter set ABCDEFGHIJKL, one possible solution is FIECB, since 6 - 9^2 + 5^3 - 3^4 + 2^5 = 1. There are actually several solutions in this case, and the combination turns out to be LKEBA. Klein thought it was safe to encode the combination within the engraving, because it could take months of effort to try all the possibilities even if you knew the secret. But of course computers didnt exist then. === Op tech directive, computer division, 2002/11/02 12:30 CST === Develop a program to