Solution.java

package Array.No_53_Maximum_Subarray;

/**
 * FileName: Solution
 * Author:   EdisonLi的家用MacBook Pro
 * Date:     2019-02-09 18:48
 * Description: Maximum Subarray
 * <p>
 * Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.
 * <p>
 * Example:
 * <p>
 * Input: [-2,1,-3,4,-1,2,1,-5,4],
 * Output: 6
 * Explanation: [4,-1,2,1] has the largest sum = 6.
 * Follow up:
 * <p>
 * If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.
 */
public class Solution {
    public int maxSubArray(int[] nums) {
        if (nums == null || nums.length == 0) {
            return 0;
        }

        int sum = nums[0];
        int max = nums[0];

        //分治法
        //判断相加后的数值 与 下一个数字的大小进行比较  若之后的数大于之前的数值 那么之前的数就不必要了 从这个数开始继续往后找
        for (int i = 1; i < nums.length; i++) {
            sum = Math.max(sum + nums[i], nums[i]);
            max = Math.max(max, sum);
        }

        return max;
    }
}