python如何求数组连续最大和的示例代码

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time  : 2020/1/29 21:59
# @Author : buu
# @Software: PyCharm
# @Blog  ：https://blog.csdn.net/weixin_44321080
def maxSubArrSum(arr):
  if arr == None or len(arr) <= 0:
    print('参数不合理！')
    return
  thisSum = 0
  maxSum = 0
  i = 0
  while i < len(arr):
    j = i
    while j < len(arr):# j 控制连续子数组包含的元素个数
      thisSum = 0
      k = i # k 表示连续子数组开始的下标
      while k < j:
        thisSum += arr[k]
        k += 1
      if thisSum > maxSum:
        maxSum = thisSum
      j += 1
    i += 1
  return maxSum


if __name__ == '__main__':
  arr = [1, -2, 4, 8, -4, 7, -1, -5]
  print('1 max sub array sum:', maxSubArrSum(arr))

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time  : 2020/1/30 10:53
# @Author : buu
# @Software: PyCharm
# @Blog  ：https://blog.csdn.net/weixin_44321080
def maxSubArrSum(arr):
  if arr == None or len(arr) <= 0:
    print('参数不合理！')
    return
  maxSum = -2 ** 31
  i = 0
  while i < len(arr): # i: 0~7
    sums = 0
    j = i
    while j < len(arr): # j: 0~7
      sums += arr[j] # sums 重复利用
      if sums > maxSum: # 每加一次就判断一次
        maxSum = sums
      j += 1
    i += 1
  return maxSum


if __name__ == '__main__':
  arr = [1, -2, 4, 8, -4, 7, -1, -5]
  print('2 max sub array sum:', maxSubArrSum(arr))

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time  : 2020/1/30 11:19
# @Author : buu
# @Software: PyCharm
# @Blog  ：https://blog.csdn.net/weixin_44321080
def maxSubArrSum(arr):
  if arr == None or len(arr) <= 0:
    print('参数不合理！')
    return
  n = len(arr)
  End = [None] * n # End[i] 表示包含 arr[i] 的最大子数组和
  All = [None] * n # All[i] 表示最大子数组和
  End[n - 1] = arr[n - 1]
  All[n - 1] = arr[n - 1]
  End[0] = All[0] = arr[0]
  i = 1
  while i < n:
    End[i] = max(End[i - 1] + arr[i], arr[i]) # i=1时若arr[0]<0,则从arr[1]重新开始
    All[i] = max(End[i], All[i - 1])
    i += 1
  return All[n - 1]


if __name__ == '__main__':
  arr = [1, -2, 4, 8, -4, 7, -1, -5]
  print('3 max sub array sum:', maxSubArrSum(arr))

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time  : 2020/1/30 11:55
# @Author : buu
# @Software: PyCharm
# @Blog  ：https://blog.csdn.net/weixin_44321080
def maxSubArrSum(arr):
  if arr == None or len(arr) <= 0:
    print('参数不合理！')
    return
  nAll = arr[0] # 最大子数组和
  nEnd = arr[0] # 包含最后一个元素的最大子数组和
  i = 1
  while i < len(arr):
    nEnd = max(nEnd + arr[i], arr[i])
    nAll = max(nEnd, nAll)
    i += 1
  return nAll


if __name__ == '__main__':
  arr = [1, -2, 4, 8, -4, 7, -1, -5]
  print('4 max sub array sum:', maxSubArrSum(arr))

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time  : 2020/1/30 12:01
# @Author : buu
# @Software: PyCharm
# @Blog  ：https://blog.csdn.net/weixin_44321080
class Test:
  def __init__(self):
    self.begin = 0 # 记录最大子数组起始位置
    self.end = 0 # 记录最大子数组结束位置

  def maxSubArrSum(self, arr):
    n = len(arr)
    maxSum = -2 ** 31 # 子数组最大值
    nSum = 0 # 包含子数组最后一位的最大值
    nStart = 0
    i = 0
    while i < n:
      if nSum < 0:
        nSum = arr[i]
        nStart = i
      else:
        nSum += arr[i]
      if nSum > maxSum:
        maxSum = nSum
        self.begin = nStart
        self.end = i
      i += 1
    return maxSum

  def getBegin(self):
    return self.begin

  def getEnd(self):
    return self.end


if __name__ == '__main__':
  arr = [1, -2, 4, 8, -4, 7, -1, -5]
  t = Test()
  print('连续最大和为:', t.maxSubArrSum(arr))
  print('begin at ', t.getBegin())
  print('end at ', t.getEnd())