53. Maximum Subarray

Kadane's Algorithm

/*
 * @lc app=leetcode id=53 lang=cpp
 *
 * [53] Maximum Subarray
 *
 * https://leetcode.com/problems/maximum-subarray/description/
 *
 * algorithms
 * Medium (51.36%)
 * Likes:    34861
 * Dislikes: 1476
 * Total Accepted:    4.5M
 * Total Submissions: 8.7M
 * Testcase Example:  '[-2,1,-3,4,-1,2,1,-5,4]'
 *
 * Given an integer array nums, find the subarray with the largest sum, and
 * return its sum.
 *
 *
 * Example 1:
 *
 *
 * Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
 * Output: 6
 * Explanation: The subarray [4,-1,2,1] has the largest sum 6.
 *
 *
 * Example 2:
 *
 *
 * Input: nums = [1]
 * Output: 1
 * Explanation: The subarray [1] has the largest sum 1.
 *
 *
 * Example 3:
 *
 *
 * Input: nums = [5,4,-1,7,8]
 * Output: 23
 * Explanation: The subarray [5,4,-1,7,8] has the largest sum 23.
 *
 *
 *
 * Constraints:
 *
 *
 * 1 <= nums.length <= 10^5
 * -10^4 <= nums[i] <= 10^4
 *
 *
 *
 * 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.
 *
 */

// @lc code=start
class Solution {
public:
    int maxSubArray(vector<int>& nums)
    {
        int curSum = 0;
        int maxSum = INT_MIN;
        for (int num : nums)
        {
            curSum = max(num, curSum + num);
            maxSum = max(maxSum, curSum);
        }
        return maxSum;
    }
};
// @lc code=end

• T: $O(N)$
• S: $O(1)$