53_Maximum_Subarray.py

'''
@Author: wangluyu
@Date: 2020-01-16 15:05:43
@LastEditors  : wangluyu
@LastEditTime : 2020-01-19 15:06:27
'''
#!/usr/bin/python
# -*- coding: utf-8 -*-
"""
Desc: 53. 最大子序和 (简单)
Author: wangluyu
Date: 2020/1/14
"""
from typing import List


class Solution:
    """
    Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.
    Example:
    Input: [-2,1,-3,4,-1,2,1,-5,4],
    Output: 6
    Explanation: [4,-1,2,1] has the largest sum = 6.
    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.
    给定一个整数数组 nums ，找到一个具有最大和的连续子数组（子数组最少包含一个元素），返回其最大和。
    示例:
    输入: [-2,1,-3,4,-1,2,1,-5,4],
    输出: 6
    解释: 连续子数组 [4,-1,2,1] 的和最大，为 6。
    进阶:
    如果你已经实现复杂度为 O(n) 的解法，尝试使用更为精妙的分治法求解。
    """
    def maxSubArray(self, nums: List[int]) -> int:
        max_sum = nums[0]
        curr_sum = 0
        for i in range(len(nums)):
            curr_sum = max(nums[i], curr_sum + nums[i])
            max_sum = max(max_sum, curr_sum)
        return max_sum


if __name__ == '__main__':
    nums = [-2,1,-3,4,-1,2,1,-5,4]
    s=Solution()
    print(s.maxSubArray(nums))