LeetCode: 53. Maximum Subarray

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53. Maximum Subarray

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

Example:

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

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.

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public int maxSubArrayDP(int[] nums) {
    // TODO Dynamic Programming
    // TODO Divide and Conquer
    return 0;
}
/**
 * Runtime: 1 ms, faster than 86.91% of Java online submissions for Maximum Subarray.
 *
 * Memory Usage: 42.1 MB, less than 5.16% of Java online submissions for Maximum Subarray.
 */
public int maxSubArray(int[] nums) {
    if (Objects.isNull(nums) || nums.length == 0) {
        return 0;
    }
    int largestSum = nums[0];
    int largestEndingHere = nums[0];
    for (int i = 1; i < nums.length; i++) {
        largestEndingHere = Math.max(largestEndingHere + nums[i], nums[i]);
        largestSum = Math.max(largestSum, largestEndingHere);
    }
    return largestSum;
}