Question

我试图为一个数字生成整数分区，但偶然发现this似乎很简短而优雅：

def partitions(n):
    # base case of recursion: zero is the sum of the empty list
    if n == 0:
        yield []
        return

    # modify partitions of n-1 to form partitions of n
    for p in partitions(n-1):
        yield [1] + p
        if p and (len(p) < 2 or p[1] > p[0]):
            yield [p[0] + 1] + p[1:]

因此，我尝试将其转换为Clojure并不幸失败了：

(defn- partitions [n]
  (if (zero? n) []
      (for [p (partitions (dec n))]
        (let [res [(concat [1] p)]]
          (if (and (not (empty? p))
                   (or (< (count p) 2) (> (second p) (first p))))
            (conj res (into [(inc (first p))] (subvec p 1)))
            res)))))

^^上面是错误的。例如：

eul=> (partitions 4)
()

我应该考虑惰性序列吗？

我在推理有关python代码时遇到麻烦，到目前为止，我对其进行转换的尝试均失败了。感谢我对解决方法的帮助。

Answer 1

Tupelo库具有Python [INFO] Installing C:\Program Files (x86)\Jenkins\workspace\helloworld-rest-app-build\pom.xml to C:\Windows\system32\config\systemprofile\.m2\repository\com\example\helloworld-rest-app\0.0.1-SNAPSHOT\helloworld-rest-app-0.0.1-SNAPSHOT.pom [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 3.991 s [INFO] Finished at: 2019-01-25T00:11:10-05:00 [INFO] ------------------------------------------------------------------------ [Pipeline] bat C:\Program Files (x86)\Jenkins\workspace\helloworld-rest-app-build>scp -i C:\Users\Nital\.ssh\LightsailDefaultKey-us-east-1.pem target\hellworld-rest-app.jar ec2-user@35.175.125.176:/home/ec2-user/app-deploys 'scp' is not recognized as an internal or external command, operable program or batch file. [Pipeline] } [Pipeline] // script [Pipeline] } [Pipeline] // withEnv [Pipeline] } [Pipeline] // stage [Pipeline] } [Pipeline] // withEnv [Pipeline] } [Pipeline] // withEnv [Pipeline] } [Pipeline] // node [Pipeline] End of Pipeline ERROR: script returned exit code 1 Finished: FAILURE函数的实现。这是翻译：

yield

Answer 2

由于分区的活动端位于最前面，因此它最好是列表而不是向量。这简化了代码的末端。

否则，坚持使用您的结构，在Clojure中，我们会得到类似...

(defn partitions [n]
  (if (zero? n)
    '(())
    (apply concat
      (for [p (partitions (dec n))]
        (let [res [(cons 1 p)]]
          (if (and (not (empty? p))
                   (or (< (count p) 2) (> (second p) (first p))))
            (conj res (cons (inc (first p)) (rest p)))
            res))))))

有效：

=> (partitions 4)
((1 1 1 1) (1 1 2) (2 2) (1 3) (4))

您哪里出错了？您无法正确解开yield。

for返回一个由一个或两个分区组成的向量序列。您必须将它们串联成一个序列。
您的基本情况也应该返回一系列分区-不尝试执行一个空分区。该算法将其视为一个空序列，将其自身沿递归链传播。因此，您的结果。

有一些小的改进要进行，但是我放弃了它们，而是更贴近您的代码。

生成整数分区-将带有yield的python代码转换为clojure

2 个答案: