# 392. Is Subsequence

![](https://4272748102-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LekNH5IywF8mjBxFcnu%2F-MehKdGMlgrejXR6w3UZ%2F-MehR7sK08WUNum7fZpR%2Fimage.png?alt=media\&token=56126893-4749-4c4f-b2c3-dd058beefb16)

![](https://4272748102-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LekNH5IywF8mjBxFcnu%2F-MehKdGMlgrejXR6w3UZ%2F-MehRHy65OGnBtTGTtBr%2Fimage.png?alt=media\&token=a1e63e04-b16e-4586-8270-0fea3cc0116f)

time: O(n)

space: O(1)

```java
class Solution {
    public boolean isSubsequence(String s, String t) {
        if (s.length() == 0) return true;
        
        int i = 0;
        for (char c : t.toCharArray()) {
            if (c == s.charAt(i)) i++;
            if (i == s.length()) return true;
        }
        return false;
    }
}


```

## follow up