遞歸與列表

Question

我遇到一個程序有問題，程序需要一個單詞，並且一次更改一個字母，將該單詞轉換爲目標單詞。雖然，請記住，根據我給出的單詞字典，轉換後的單詞必須是合法的單詞。

我很難弄清楚如何使它遞歸。該程序對其必須採取的步驟數量有限制。

編輯：我不能讓持有人名單全球。

到目前爲止我的代碼：

def changeling(word,target,steps): 
    holderlist=[] 
    i=0 
    if steps<0 and word!=target: 
     return None 

    if steps!=-1: 
     for items in wordList: 
      if len(items)==len(word): 
       i=0 

       if items!=word: 
        for length in items: 

         if i==1: 
          if items[1]==target[1] and items[0]==word[0] and items[2:]==word[2:]: 
           if items==target: 
            print "Target Achieved" 
            holder.list.append(target) 
           holderlist.append(items) 
           changeling(items,target,steps-1) 

         elif i>0 and i<len(word)-1 and i!=1: 
          if items[i]==target[i] and items[0:i]==word[0:i] and items[i+1:]==word[i+1:]: 
           if items==target: 
            print "Target Achieved" 
           holderlist.append(items) 
           changeling(items,target,steps-1) 

         elif i==0: 
          if items[0]==target[0] and items[1:]==word[1:]: 
           if items==target: 
            print "Target Achieved" 
           holderlist.append(items) 
           changeling(items,target,steps-1) 

         elif i==len(word)-1: 
          if items[len(word)-1]==target[len(word)-1] and items[0:len(word)-1]==word[0:len(word)-1]: 
           if items==target: 
            print "Target Achieved" 
           holderlist.append(items) 
           changeling(items,target,steps-1) 
         else: 
          changeling(None,None,steps-1) 

         i+=1 

    return holderlist 

我最大的問題是，我的控股名單holderlist刷新每次我嘗試讓程序遞歸。

我可以解決它，如果我手動輸入數據。這是我想要的程序來做：

changeling("find","lose",4) 
gives me: 
['fine','fond'] 
the program should then do: 
changeling('fine','lose',3) 
gives me: 
['line'] 
changeling('line','lose',2) 
gives me: 
['lone'] 
changeling('lone','lose',1) 
gives me: 
['lose'] 
Target Achieved 

Answer 1

可能像

def distx(w1,w2): 
    if len(w1) != len(w2):return 100000 
    score=0 
    for i in range(len(w1)): 
     score += int(w1[i] != w2[i]) 
    return score 


word_list = ["fine","fond","line","lose","lone"] 

def changeling(guess,target,steps): 
    my_steps = [] 
    print "Guess:",guess 
    if target == guess:return [guess] 
    try:word_list.remove(guess) 
    except:pass 
    my_steps.append(guess) 
    if target != guess and steps >= 0: 
     this_step = [] 
     one_step_away = [w for w in word_list if distx(guess,w) == 1] 
     for k in one_step_away: 
      print "  %s->"%guess,k 
      this_step.append(changeling(k,target,steps-1)) 
    my_steps.append(this_step) 
    return my_steps 
tmp = changeling("find","lose",4) 
print tmp