Add solution for Maximun subarray

Author: KwonNayeon

maximum-subarray/KwonNayeon.py

@@ -0,0 +1,31 @@
+"""
+Conditions:
+- 1 <= nums.length <= 10^5
+- -10^4 <= nums[i] <= 10^4
+
+Time Complexity: O(n)
+- 배열을 한 번만 순회함
+
+Space Complexity: O(1)
+- 두 변수 이외에 추가 공간을 사용하지 않음
+
+풀이방법: 
+1. Base case: If nums is empty, return 0
+2. Initialize variables (current_sum and max_sum as the first value in the array)
+3. Traverse from the value at 1st index to the last, update current_sum
+   - Decide whether to add the current value (num) to the existing subarray or start a new one
+4. Update max_sum
+   - Choose the larger between the updated current_sum and the previous max_sum
+"""
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        if not nums:
+            return 0
+
+        current_sum = max_sum = nums[0]
+
+        for num in nums[1:]:
+            current_sum = max(num, current_sum + num)
+            max_sum = max(current_sum, max_sum)
+
+        return max_sum