53.maximum-subarray.cpp

/*
 * @lc app=leetcode id=53 lang=cpp
 *
 * [53] Maximum Subarray
 *
 * https://leetcode.com/problems/maximum-subarray/description/
 *
 * algorithms
 * Easy (49.61%)
 * Likes:    25580
 * Dislikes: 1162
 * Total Accepted:    2.8M
 * Total Submissions: 5.6M
 * Testcase Example:  '[-2,1,-3,4,-1,2,1,-5,4]'
 *
 * 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 <= 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 ans =0, cur =0,maxelem = INT_MIN;
        for(int i:nums){
            cur +=i;
            cur = max(0,cur);
            ans = max(cur,ans);
            maxelem = max(i,maxelem);
        }
        return(maxelem<0)? maxelem:ans;
    }
};
// @lc code=end