- Difficulty: Easy.
- Related Topics: Two Pointers, String, Dynamic Programming.
- Similar Questions: Number of Matching Subsequences, Shortest Way to Form String, Append Characters to String to Make Subsequence, Make String a Subsequence Using Cyclic Increments.
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?
## Solution
```javascript
/**
* @param {string} s
* @param {string} t
* @return {boolean}
*/
var isSubsequence = function(s, t) {
var j = 0;
for (var i = 0; i < s.length; i++) {
while (s[i] !== t[j] && j < t.length - 1) j++;
if (s[i] != t[j]) return false;
j++;
}
return true;
};
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(1).