[Algorithm] LeetCode 53. Maximum Subarray

53. Maximum Subarray

Medium

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Given an integer array nums, find the subarray with the largest sum, and return its sum.

 

Example 1:

Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
Output: 6
Explanation: The subarray [4,-1,2,1] has the largest sum 6.

Example 2:

Input: nums = [1]
Output: 1
Explanation: The subarray [1] has the largest sum 1.

Example 3:

Input: nums = [5,4,-1,7,8]
Output: 23
Explanation: The subarray [5,4,-1,7,8] has the largest sum 23.

 

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104

 

Follow up: If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

 

Solution:

class Solution {
    public int maxSubArray(int[] nums) {
        int n = nums.length;
        int currentMax = nums[0];
        int globalMax = currentMax;
        
        if (n == 1) return currentMax;
        for (int i = 1; i < n; i++) {
            currentMax = Math.max(currentMax + nums[i], nums[i]);
            globalMax = Math.max(currentMax, globalMax);
        }
        
        return globalMax;
    }
}

 

전형적인 카데인 알고리즘(Kadane's Algorithm) 문제이다.