June Leetcoding Challenge(6.9)

LeetCode六月挑战 Is Subsequence　LeetCode 392

Solution
Given a string s and a string t, check if s is subsequence of t.

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

Follow up:
If there are lots of incoming S, say S1, S2, … , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?

Credits:
Special thanks to @pbrother for adding this problem and creating all test cases.

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 <= 10^4
Both strings consists only of lowercase characters.

思路

• Java做法： 采用两个指针，当匹配到相同的，s和t的指针移动到下一位，如果不匹配，将t的指针移动到下一位继续匹配。
• python做法：将s转换为list q，如果q本身为空，返回true。如果q不为空，不断匹配，如果匹配到相同的字符，就把他从list q中删除。匹配到t的最后一位，如果q为空，返回true。

代码

java

class Solution {
    public boolean isSubsequence(String s, String t) {
        if(s.length() ==0&& t.length() !=0)
            return true;
        char c1[]= s.toCharArray();
        char c2[]= t.toCharArray();
        
        int i = 0,j=0;
        while(i<c1.length && j<c2.length){
            if(c1[i] == c2[j]){
                i++;
                j++;
                continue;
            }else{
                j++;
                continue;
            }  
        }
        return i==(c1.length);
    }
}

python

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        q = list(s);
        for c in t:
            if not q:
                return True;
            if c == q[0]:
                q.pop(0);
        return not q;