python中常用的算法

算法

查找

• 顺序查找

> def sequential_Search(item,list): 	
>		i = 0 	
>		while i < len(list): 		
> 			if item == list[i]:
> 				return i 		
> 			i += 1 	
>		return -1

• 二分查找(折半查找)
  • 循环实现：

def binarch_sarch(item,list):
	 start = 0
	 stop = len(list1)-1
	 while start <= stop:
			 mid = (start+stop)//2
			 if item == list[mid]:
			 	return mid
			 elif item > list[mid]:
				start = mid + 1
			 else:
				stop = mid - 1
	 return -1

• 递归实现：

def binarch_sarch(start,stop,item,list):
    mid = (start+stop)//2
    if start > stop:
        return -1
    if item == list[mid]:
        return mid
    elif item > list[mid]:
        return binarch_sarch(mid + 1,stop,item,list)
    else:
        return binarch_sarch(start, mid - 1, item, list)

• 排序
  • 冒泡排序

 def bubble_sort(nums):
        for i in range(len(nums) - 1):  # 这个循环负责设置冒泡排序进行的次数
            for j in range(len(nums) - i - 1):  # j为列表下标
                if nums[j] > nums[j + 1]:
                    nums[j], nums[j + 1] = nums[j + 1], nums[j]
        return nums

• 选择排序

   def selection_sort(list2):
      for i in range(0, len (list2)-1):
        min = i
        for j in range(i + 1, len(list2)):
          if list2[j] < list2[min]:
            min = j
         list2[i], list2[min] = list2[min], list2[i]  # swap