Maximum suborder sum problem

Recently, I encountered a lot of problems when I was looking for an internship and brushing the questions. There are some frustrations that I still report an error after 2 hours of coding, and I also have the loneliness of overcoming 100%. I would like to record one or two here and share my encouragement with you.

Given an integer array nums , find a contiguous subarray with the largest sum (the subarray contains at least one element), and return its largest sum (from leetcode53 problem).

Write a brute force recursion first

class Solution {
    public int maxSubArray(int[] nums) {	
    	return getMax(nums,nums.length-1);
    }

  private int getMax(int[] nums, int index) {
	if(index=0) {
	    return nums[0];
	}
        return Math.max(chosed(nums,index-1)+nums[index],getMax(nums, index-1));
    }
	
  private int chosed(int[] nums,int index) {
        if(index<0) {
		return 0;
	}
	return Math.max(chosed(nums, index-1)+nums[index],0);
  }
}

OJ actually passed. . .

I have been thinking about this recursive dynamic programming for a long time, and I feel that my thinking has become rigid. Baidu took a look and referred to the blogger.window rain tree snowThe method is written in O(n).

class Solution {
	public int maxSubArray(int[] nums) {
		int sum = 0;
		int maxSum =Integer.MIN_VALUE;
        	//find the maximum value in nums
		for (int i = 0; i < nums.length; i++) {
			if(nums[i]>maxSum) {
				maxSum = nums [i];
			}
		}
		//When a number plus the previous sum is greater than the maximum, it is assigned, and it is impossible to be the start bit when it is less than zero
		for (int i = 0; i < nums.length; i++) {
			sum += nums[i];
			if(sum>maxSum) {
				maxSum = sum;
			}else if(sum<0){
				sum = 0;
			}
		}
		return maxSum;
	}
}

oj: 13ms, I don't know why, I can't insert pictures

, Okay, please correct me.

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