【朱迪的LeetCode刷题笔记】392. Is Subsequence 判断子序列 #Easy #Python

Judie

Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not).

Example 1:
Input: s = "abc", t = "ahbgdc"
Output: true

Example 2:
Input: s = "axc", t = "ahbgdc"
Output: false

Constraints:
0 <= s.length <= 100
0 <= t.length <= 104
s and t consist only of lowercase English letters.

Follow up:
Suppose there are lots of incoming s, say s1, s2, ..., sk where k >= 109, and you want to check one by one to see if t has its subsequence. In this scenario, how would you change your code?

1. class Solution(object):
   
2.     def isSubsequence(self, s, t):
   
3.         """
   
4.         :type s: str
   
5.         :type t: str
   
6.         :rtype: bool
   
7.         """

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Judy
python

1. class Solution(object):
   
2.     def isSubsequence(self, s, t):
   
3.         """
   
4.         :type s: str
   
5.         :type t: str
   
6.         :rtype: bool
   
7.         """
   
8. 
   
9.         j = 0
   
10.         for x in s:
    
11.             idx = t[j:].find(x)
    
12.             if idx == -1:
    
13.                 return False
    
14.             j += idx + 1  
    
15.         
    
16.         return True

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Gray
c++ better version?!

1. class Solution {
   
2. public:
   
3.     bool isSubsequence(string s, string t) {
   
4.         if(s == "") return true;
   
5.         if(t == "") return false;
   
6.         int index = 0;
   
7.         for(int i = 0; i < t.size(); i++){
   
8.            if(s[index]==t[i]){
   
9.                index++;
   
10.            }
    
11.            if(index==s.size()){
    
12.                return true;
    
13.            }
    
14.         }
    
15.         return false;
    
16.     }
    
17. };

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