Maximum Subarray

Description

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.

Code

Java

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

DP

class Solution {
    public int maxSubArray(int[] nums) {
        int[] dp = new int[nums.length];
        dp[0] = nums[0];
        int max = nums[0];
        for (int i = 1; i < nums.length; i++) {
            dp[i] = dp[i - 1] > 0 ? dp[i - 1] + nums[i] : nums[i];
            max = Math.max(max, dp[i]);
        }
        return max;
    }
}