add 918

Author: luliyucoordinate

README.md

@@ -135,4 +135,5 @@ LeetCode
 |0455|[Assign Cookies](https://leetcode.com/problems/assign-cookies/) | c | [c++](./src/0455-Assign-Cookies/0455.cpp) |[python](./src/0455-Assign-Cookies/0455.py)|||Easy|
 |0474|[Ones and Zeroes](https://leetcode.com/problems/ones-and-zeroes/) | c | [c++](./src/0474-Ones-and-Zeroes/0474.cpp) |[python](./src/0474-Ones-and-Zeroes/0474.py)|||Medium|
 |0494|[Target Sum](https://leetcode.com/problems/target-sum/) | c | [c++](./src/0494-Target-Sum/0494.cpp) |[python](./src/0494-Target-Sum/0494.py)|||Medium|
-|0917|[Reverse Only Letters](https://leetcode.com/problems/reverse-only-letters/) | c | [c++](./src/0917-Reverse-Only-Letters/0917.cpp) |[python](./src/0917-Reverse-Only-Letters/0917.py)|||Easy|
+|0917|[Reverse Only Letters](https://leetcode.com/problems/reverse-only-letters/) | c | [c++](./src/0917-Reverse-Only-Letters/0917.cpp) |[python](./src/0917-Reverse-Only-Letters/0917.py)|||Easy|
+|0918|[Maximum Sum Circular Subarray](https://leetcode.com/problems/maximum-sum-circular-subarray/) | c | [c++](./src/0918-Maximum-Sum-Circular-Subarray/0918.cpp) |[python](./src/0918-Maximum-Sum-Circular-Subarray/0918.py)|||Medium|

src/0918-Maximum-Sum-Circular-Subarray/0918.cpp

@@ -0,0 +1,42 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using  namespace std;
+
+static int x = []() {std::ios::sync_with_stdio(false); cin.tie(0); return 0; }();
+class Solution 
+{
+public:
+    int maxSubarraySumCircular(vector<int>& A) 
+    {
+        int max_A = *max_element(A.begin(), A.end());
+        if (max_A < 0) return max_A;
+        int result1 = kadane(A);
+        int result2 = 0;
+        for (unsigned int i = 0; i < A.size(); ++i)
+        {
+            result2 += A[i];
+            A[i] = -A[i];
+        }
+        result2 += kadane(A);
+        return max(result1, result2);
+    }
+private:
+    int kadane(vector<int>& nums)
+    {
+        int cur = 0, result = 0;
+        for (auto& num :nums)
+        {
+            cur += num;
+            if (cur < 0) cur = 0;
+            if (result < cur) result = cur;
+        }
+        return result;
+    }
+};
+int main()
+{
+    vector<int> A = {-2,-3,-1};
+    cout << Solution().maxSubarraySumCircular(A);
+    return 0;
+}

src/0918-Maximum-Sum-Circular-Subarray/0918.py

@@ -0,0 +1,35 @@
+class Solution:
+    def maxSubarraySumCircular(self, a):
+        """
+        :type A: List[int]
+        :rtype: int
+        """      
+        def kadane(nums): 
+            cur, result = 0, 0
+            for num in nums: 
+                cur += num 
+                if cur < 0: 
+                    cur = 0
+                if result < cur: 
+                    result = cur 
+            return result 
+        
+        max_a = max(a)
+        if max_a < 0:
+            return max_a
+
+        len_a = len(a) 
+        result1 = kadane(a) 
+        result2 = 0
+        for i in range(len_a): 
+            result2 += a[i] 
+            a[i] = -a[i] 
+
+        result2 += kadane(a) 
+
+        return max(result1, result2)
+        
+
+if __name__ == "__main__":
+    A = [-2, -3, -1]
+    print(Solution().maxSubarraySumCircular(A))