Question

给定一个字符串

s = "dog cat bat cat dog dog"

找到两次出现的第一个单词。答案：猫

到目前为止，我有以下代码：

def first_word(string):
    for word in string.split():
        print(word)

first_word("dog cat bat cat dog dog")

Answer 1

首先，您的功能名称不具有描述性。我会将其更改为first_repeated_word。

分裂部分很好，但你需要记住你已经看过的单词。将单词添加到set（因为它支持快速查找）并查看您是否已经看到它会起作用：

def first_repeated_word(string):
    processed = set()
    for word in string.split():
        if word in processed:
            # this will immediatly end the function and return the repeated word
            return word  
        # Add the word to the set.
        processed.add(word)  
    # You need to consider the case when no repeated word was found, best
    # to throw an exception
    raise ValueError('no repeated word found')

功能的实际测试：

>>> first_repeated_word("dog cat bat cat dog dog")
'cat'

我实际上有一个第三方模块可以做到这一点（更有效率）：iteration_utilities.duplicates

>>> from iteration_utilities import duplicates
>>> your_string = "dog cat bat cat dog dog"
>>> next(duplicates(your_string.split()))
'cat'

Answer 2

你只需要你的循环来检查你之前是否看过那个单词。像这样：

def first_repeat(string):
    previous = []
    for word in string.split():
        if word in previous:
            print(word)
            break
        else:
            previous.append(word)

说明：对于每个单词，检查您之前是否已经看到它（它是否在previous中），如果是，则打印该单词并停止循环，如果它< em>不是，将当前单词添加到以前单词列表中。

Answer 3

>>> found_twice = False
>>> seen = set()
>>> i = 0
>>> s = s.split()
>>> s
['dog', 'cat', 'bat', 'cat', 'dog', 'dog']
>>> while not found_twice:
...     if s[i] not in seen:
...         seen.add(s[i])
...     else:
...         print(s[i])
...         found_twice = True
...     i += 1
... 
cat

或者：

>>> seen = set()
>>> for x in s:
...     if x not in seen:
...         seen.add(x)
...     else:
...         print(x)
...         break
...     
... 
cat

有很多方法可以迭代一系列元素并跟踪你已经看过的内容。＆＃34;

Answer 4

这有效：

def find_first_duplicate(s):
    s_list = s.split(' ')  # split string everytime there is a space
    l = []
    for item in s_list:
        if item in l:
            # We found the first duplicate!
            return item
        else:
            # Otherwise add to list and try again
            l.append(item)
    return 'No Duplicates'

Answer 5

这可以解决

def first_word(string):  # string is the words you pass
    a= string.split()    # a is the list of individual words
    b=[]                 # b is an empty list  
    for item in a:
        if item not in b:
            b.append(item) # here we add unique words to b
        else:       # if a word gets repeated for the first time it will print the word 
            print item
            break          # since we printed the first repeated word we break out of loop

first_word('cat dog bird cat dog')

解决方案：

cat

找到字符串中出现两次的第一个单词

5 个答案: