Python实现最大子序和的方法示例

class Solution:
  def maxSubArray(self, nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    l = len(nums)
    i = 0
    result = nums[0]
    while i < l:
      sums = []
      temp = 0
      for j in range(i, l):
        temp+=nums[j]
        sums.append(temp)
      if result < max(sums):
        result = max(sums)
      i+=1
    return result

  l = len(nums)
    i = 0
    result = nums[0]
    while i < l:
      temp = 0
      for j in range(i, l):
        temp+=nums[j]
        if result < temp:
          result = temp
      i+=1
    return result

def maxC2(ls,low,upp): 
  #"divide and conquer" 
  if ls is None: return 0 
  elif low==upp: return ls[low] 

  mid=(low+upp)/2 #notice: in the higher version python, “/” would get the real value 
  lmax,rmax,tmp,i=0,0,0,mid 
  while i>=low: 
    tmp+=ls[i] 
    if tmp>lmax: 
      lmax=tmp 
    i-=1 
  tmp=0 
  for k in range(mid+1,upp): 
    tmp+=ls[k] 
    if tmp>rmax: 
      rmax=tmp 
  return max3(rmax+lmax,maxC2(ls,low,mid),maxC2(ls,mid+1,upp)) 

def max3(x,y,z): 
  if x>=y and x>=z: 
    return x 
  return max3(y,z,x) 

   l = len(nums)
    i = 0
    sum = 0
    MaxSum = nums[0]
    while i < l:
      sum+=nums[i]
      if sum > MaxSum:
          MaxSum = sum
      if sum < 0:
        sum = 0
      i+=1
    return MaxSum

 sum = 0
    MaxSum = nums[0]
    for i in range(len(nums)):
      sum += nums[i]
      if sum > MaxSum:
        MaxSum = sum
      if sum < 0:
        sum = 0
    return MaxSum

MaxSum = sum