add max sum contigous subsequence (#1537)

* add max sum contigous subsequence

* fix typo

* Add doctest and type hints

* Create autoblack.yml

.github/workflows/autoblack.yml

@@ -0,0 +1,34 @@
+# GitHub Action that uses Black to reformat the Python code in an incoming pull request.
+# If all Python code in the pull request is complient with Black then this Action does nothing.
+# Othewrwise, Black is run and its changes are committed back to the incoming pull request.
+# https://github.com/cclauss/autoblack
+
+name: autoblack
+on: [pull_request]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      max-parallel: 1
+      matrix:
+        python-version: [3.7]
+    steps:
+      - uses: actions/checkout@v1
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v1
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install psf/black
+        run: pip install black
+      - name: Run black --check .
+        run: black --check .
+      - name: If needed, commit black changes to the pull request
+        if: failure()
+        run: |
+          black .
+          git config --global user.name 'autoblack'
+          git config --global user.email 'cclauss@users.noreply.github.com'
+          git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/$GITHUB_REPOSITORY
+          git checkout $GITHUB_HEAD_REF
+          git commit -am "fixup: Format Python code with psf/black"
+          git push

dynamic_programming/max_sum_contigous_subsequence.py

@@ -0,0 +1,20 @@
+def max_subarray_sum(nums: list) -> int:
+    """
+    >>> max_subarray_sum([6 , 9, -1, 3, -7, -5, 10])
+    17
+    """
+    if not nums:
+        return 0
+    n = len(nums)
+    s = [0] * n
+    res, s, s_pre = nums[0], nums[0], nums[0]
+    for i in range(1, n):
+        s = max(nums[i], s_pre + nums[i])
+        s_pre = s
+        res = max(res, s)
+    return res
+
+
+if __name__ == "__main__":
+    nums = [6, 9, -1, 3, -7, -5, 10]
+    print(max_subarray_sum(nums))