Add longest common substring (#7488)

* added longest common substring

* added retrun type hint

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* changed t1, t2 to text1, text2

* Update longest_common_substring.py

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Chris O <[email protected]>

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Chris O <[email protected]>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* applied suggested changes

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Caeden Perelli-Harris <[email protected]>

* removed space between line

* return longest common substring

* Update dynamic_programming/longest_common_substring.py

Co-authored-by: Christian Clauss <[email protected]>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: Caeden Perelli-Harris <[email protected]>
Co-authored-by: Chris O <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <[email protected]>