小知识，大挑战！本文正在参与“程序员必备小知识”创作活动
描述
Given an array of strings patterns and a string word, return the number of strings in patterns that exist as a substring in word.
A substring is a contiguous sequence of characters within a string.
Example 1:
Input: patterns = ["a","abc","bc","d"], word = "abc"
Output: 3
Explanation:
- "a" appears as a substring in "abc".
- "abc" appears as a substring in "abc".
- "bc" appears as a substring in "abc".
- "d" does not appear as a substring in "abc".
3 of the strings in patterns appear as a substring in word.
Example 2:
Input: patterns = ["a","b","c"], word = "aaaaabbbbb"
Output: 2
Explanation:
- "a" appears as a substring in "aaaaabbbbb".
- "b" appears as a substring in "aaaaabbbbb".
- "c" does not appear as a substring in "aaaaabbbbb".
2 of the strings in patterns appear as a substring in word.
Example 3:
Input: patterns = ["a","a","a"], word = "ab"
Output: 3
Explanation: Each of the patterns appears as a substring in word "ab".
Note:
1 <= patterns.length <= 100
1 <= patterns[i].length <= 100
1 <= word.length <= 100
patterns[i] and word consist of lowercase English letters.
解析
根据题意，就是给出了一个列表 patterns ，里面有很多模版元素，又给出了一个单词 word ，要求我们找出有多少个模版在 word 中出现过，这个思路很简单，就是找子字符串的个数。直接遍历 patterns 中的每个元素，然后判断是否在 word 中出现过，将出现过的 pattern 进行计数，最后返回即可。
解答
class Solution(object):
def numOfStrings(self, patterns, word):
"""
:type patterns: List[str]
:type word: str
:rtype: int
"""
result = 0
for p in patterns:
if p in word:
result += 1
return result
运行结果
Runtime: 20 ms, faster than 81.60% of Python online submissions for Number of Strings That Appear as Substrings in Word.
Memory Usage: 13.7 MB, less than 18.40% of Python online submissions for Number of Strings That Appear as Substrings in Word.
解析
其实直接用 python 的内置函数 sum 也比较方便，一行代码就解决了，这真的是人生苦短我用 python 。
sum 函数本来就是对序列进行求和计算，例如：
>>>sum([1,2,3])
6
如果对布尔类型的列表用此函数，会统计为 True 的个数，例如：
>>>sum([True,True,False])
2
本题就是用到了 sum 函数的第二种计算方法，用来直接对 pattern in word 这个布尔结果进行计数，得到的结果即为答案。
解答
class Solution(object):
def numOfStrings(self, patterns, word):
"""
:type patterns: List[str]
:type word: str
:rtype: int
"""
return sum(pattern in word for pattern in patterns)
运行结果
Runtime: 20 ms, faster than 81.60% of Python online submissions for Number of Strings That Appear as Substrings in Word.
Memory Usage: 13.5 MB, less than 91.59% of Python online submissions for Number of Strings That Appear as Substrings in Word.
原题链接：leetcode.com/problems/nu…
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