> For the complete documentation index, see [llms.txt](https://soumyajit4419.gitbook.io/ds-algo/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://soumyajit4419.gitbook.io/ds-algo/strings/2.-is-subsequence.md).

# 2. Is Subsequence

Given two strings `s` and `t`, check if `s` is a **subsequence** of `t`.

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
```

## Solution: (Greedy)

```cpp
class Solution
{
public:
    bool isSubsequence(string s, string t)
    {

        int n = t.length();
        int m = s.length();

        int i = 0, j = 0;

        while (i < n)
        {

            if (s[j] == t[i])
            {
                j++;
                i++;
            }
            else
            {
                i++;
            }
        }

        if (j == m)
        {
            return true;
        }

        return false;
    }
};
```

**Time Complexity: O(n + m)**