迭代解决方案: - 查找字符串排列

Question

我阅读了这个简单而优雅的python解决方案,用于查找给定字符串的所有排列.它是递归的.基于此,我尝试在python中实现迭代解决方案.

以下是我的代码.但它只适用于3个字符串:(试图看看递归基本情况条件和递归条件如何转换为迭代(非递归)任何指针都有助于使迭代解决方案有效.(基于此算法或任何其他)

def  permutations_iter(word):
while True:
    perms = []
    result = []

    char = word[0]
    new_word = word[1:]

    if len(new_word)==2: 
        perms = [new_word,''.join(reversed(new_word))]

    for perm in perms: 
        #insert the character into every possible location 
        for i in range(len(perm)+1): 
            result.append(perm[:i] + char + perm[i:]) 
    return result

    if len(new_word)==2:
        break;


   #example code to call this iterative function        
   print permutations_iter("LSE")   

Answer 1

您可以使用堆栈将每个递归转换为迭代.但在这种情况下,由于算法非常简单,因此更简单.

def perms(word):
    stack = list(word)
    results = [stack.pop()]
    while len(stack) != 0:
        c = stack.pop()
        new_results = []
        for w in results:
            for i in range(len(w)+1):
                new_results.append(w[:i] + c + w[i:])
        results = new_results
    return results

对于递归到迭代的更一般转换,使用堆栈读取此内容