DSA/Maximum_Sum_Circular_Subarray.java at main · adi-gp/DSA · GitHub

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/*

Given a circular integer array nums of length n, return the maximum possible sum of a non-empty subarray of nums.

A circular array means the end of the array connects to the beginning of the array. Formally, the next element of nums[i] is nums[(i + 1) % n] and the previous element of nums[i] is nums[(i - 1 + n) % n].

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


Example 1:

Input: nums = [1,-2,3,-2]
Output: 3
Explanation: Subarray [3] has maximum sum 3.
Example 2:

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

Input: nums = [-3,-2,-3]
Output: -2
Explanation: Subarray [-2] has maximum sum -2.


Constraints:

n == nums.length
1 <= n <= 3 * 104
-3 * 104 <= nums[i] <= 3 * 104

*/

class Maximum_Sum_Circular_Subarray {
    public int maxSubarraySumCircular(int[] nums) {
        int n = nums.length;
        int best = nums[0];
        int worst = nums[0];
        int bestresult = nums[0];
        int worstresult = nums[0];
        int sum = nums[0];
        for(int i = 1 ; i< n ; i++){
            sum = sum + nums[i];
            int oldbest = best;
            int oldworst = worst;
            best = Math.max(oldbest+nums[i], nums[i]);
            worst = Math.min(oldworst + nums[i], nums[i]);
            bestresult = Math.max(bestresult , best);
            worstresult = Math.min(worstresult , worst);
        }
        if(bestresult <0){
            return bestresult;
        }
        else{
            return Math.max(bestresult, (sum-worstresult));
        }

    }
}