【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?

class Solution(object):
    def isSubsequence(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """

Judy
python

class Solution(object):
    def isSubsequence(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """

        j = 0
        for x in s:
            idx = t[j:].find(x)
            if idx == -1:
                return False
            j += idx + 1  
        
        return True

Gray
c++ better version?!

class Solution {
public:
    bool isSubsequence(string s, string t) {
        if(s == "") return true;
        if(t == "") return false;
        int index = 0;
        for(int i = 0; i < t.size(); i++){
           if(s[index]==t[i]){
               index++;
           }
           if(index==s.size()){
               return true;
           }
        }
        return false;
    }
};