LeetCode-in-All
53. Maximum Subarray
Easy
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.
Solution
class Solution {
/**
* @param Integer[] $nums
* @return Integer
*/
public function maxSubArray($nums) {
$maxi = PHP_INT_MIN;
$sum = 0;
foreach ($nums as $num) {
// calculating sub-array sum
$sum += $num;
$maxi = max($sum, $maxi);
if ($sum < 0) {
// there is no point to carry a -ve subarray sum. hence setting to 0
$sum = 0;
}
}
return $maxi;
}
}