53.maximum-subarray.python3.py

#
# [53] Maximum Subarray
#
# https://leetcode.com/problems/maximum-subarray/description/
#
# algorithms
# Easy (41.14%)
# Total Accepted:    367K
# Total Submissions: 890.6K
# 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.
# 
# 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.
# 
#


class Solution:
    def maxSubArray(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        length = len(nums)
        if length < 2:
            return sum(nums)

        max_res = pre_res = nums[0]
        for i in range(1, length):
                pre_res = nums[i] if pre_res <= 0 else nums[i] + pre_res
                max_res = max(max_res, pre_res)

        return max_res