Maximum Sum Circular Subarray

Maximum Sum Circular Subarray

Given a circular array C of integers represented by A, find the maximum possible sum of a non-empty subarray of C.

Here, a circular array means the end of the array connects to the beginning of the array.  (Formally, C[i] = A[i] when 0 <= i < A.length, and C[i+A.length] = C[i] when i >= 0.)

Also, a subarray may only include each element of the fixed buffer A at most once.  (Formally, for a subarray C[i], C[i+1], ..., C[j], there does not exist i <= k1, k2 <= j with k1 % A.length = k2 % A.length.)

 

Example 1:

Input: [1,-2,3,-2]
Output: 3
Explanation: Subarray [3] has maximum sum 3

Example 2:

Input: [5,-3,5]
Output: 10
Explanation: Subarray [5,5] has maximum sum 5 + 5 = 10

Example 3:

Input: [3,-1,2,-1]
Output: 4
Explanation: Subarray [2,-1,3] has maximum sum 2 + (-1) + 3 = 4

Example 4:

Input: [3,-2,2,-3]
Output: 3
Explanation: Subarray [3] and [3,-2,2] both have maximum sum 3

Example 5:

Input: [-2,-3,-1]
Output: -1
Explanation: Subarray [-1] has maximum sum -1

 

Note:

1. -30000 <= A[i] <= 30000
2. 1 <= A.length <= 30000

 class Solution {
public:
    int maxSum(vector<int> v)
    {
        int global=*max_element(v.begin(),v.end()),curr=0;
        for(int i=0;i<v.size();++i)
        {
            curr+=v[i];
            global=max(global,curr);
            curr=max(curr,0);
        }
        return global;
    }
    int minSum(vector<int> v)
    {
        int global=0,curr=0;
        for(int i=0;i<v.size();++i)
        {
            curr+=v[i];
            global=min(global,curr);
            curr=min(curr,0);
        }
        return global;
    }
    int maxSubarraySumCircular(vector<int>& A) {
        int sum=0;
        for(auto i: A)
            sum+=i;
        int mx=maxSum(A);
        int mn=minSum(A);
        sum=sum+abs(mn);
        if(sum==0)
            return mx;
        return max(sum,mx);
    }
};