Easy_Question2 : 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.

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

Solution:

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

Complexity Analysis

• Time complexity: $O(n)$. Only a single pass is needed.

• Space complexity: $O(1)$. Only two variables are used.