[LeetCode] DP - 53. Maximum Subarray

문제

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

A subarray is a contiguous part of an array.

 

Example 1:

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

Example 2:

Input: nums = [1]
Output: 1

Example 3:

Input: nums = [5,4,-1,7,8]
Output: 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.

코드

/**
 * @param {number[]} nums
 * @return {number}
 */
function maxSubArray(nums) {
    let prev = 0;
    let max = -Infinity;

    for(let i = 0; i < nums.length; i++) {
        // prev는 이전 prev에 현재값을 더한거이거나
        // prev에 현재값을 더한게
        // prev를 현재값으로 새로시작한다
        prev = Math.max(prev + nums[i], nums[i])
        max = Math.max(max, prev);
    }

    return max;
}