您好,登錄后才能下訂單哦!
這篇文章主要講解了Python二分查找算法的實(shí)現(xiàn)方法,內(nèi)容清晰明了,對(duì)此有興趣的小伙伴可以學(xué)習(xí)一下,相信大家閱讀完之后會(huì)有幫助。
先來(lái)看個(gè)用Python實(shí)現(xiàn)的二分查找算法實(shí)例
import sys def search3(a,m): low = 0 high = len(a) - 1 while(low <= high): mid = (low + high)/2 midval = a[mid] if midval < m: low = mid + 1 elif midval > m: high = mid - 1 else: print mid return mid print -1 return -1 if __name__ == "__main__": a = [int(i) for i in list(sys.argv[1])] m = int(sys.argv[2]) search3(a,m)om/weixin.html#_labeldown
運(yùn)行:
administrator@ubuntu:~/Python$ python test_search3.py 123456789 4
注:
1.'__':由于python的類(lèi)成員都是公有、公開(kāi)的被存取public,缺少像正統(tǒng)面向?qū)ο笳Z(yǔ)言的私有private屬性。
于是就用__來(lái)將就一下,模擬私有屬性。這些__屬性往往是內(nèi)部使用,通常情況下不用改寫(xiě)。也不用讀取。
加上2個(gè)下劃線的目的,一是不和普通公有屬性重名沖突,二是不讓對(duì)象的使用者(非開(kāi)發(fā)者)隨意使用。
2.__name__ == "__main__"表示程序腳本是直接被執(zhí)行的.
如果不等于表示腳本是被其他程序用import引入的.則其__name__屬性被設(shè)為模塊名
Python采用二分查找找出數(shù)字的下標(biāo)
要考慮有重復(fù)數(shù)字的情況
class Solution(object): def searchRange(self, nums, target): """ :type nums: List[int] :type target: int :rtype: List[int] def binary_search(start,end,value): while end>=start: mid = (start+end)//2 print(mid) if nums[mid]>target: end = mid-1 elif nums[mid]<target: start="mid+1" else:="" if="" value="=-1:" mid-1="">=start and nums[mid+value] == target: end = mid+value else: return mid else: if mid+1<=end and nums[mid+value] == target: start = mid+value return -1 a=binary_search(0,len(nums)-1,-1) b=binary_search(0,len(nums)-1,1) return [a,b] a = Solution() l = [2,2] print(a.searchRange(l,2)) </target:>
二分算法的定義不在多說(shuō)了
import sys source = [1,2,3,4,5,6,7,8,9,10] #must be in order des = int(sys.argv[1]) low = 0 high = len(source) - 1 targetIndex = -1 print "des=",des while low <= high: middle = (low + high)/2 if des == source[middle]: targetIndex = middle break elif des < source[middle]: high = middle -1 print "middle element[index=",middle,",value=",source[middle],"] is bigger than des, continue search from[",low,"to",high,"]" else: low = middle + 1 print "middle element[index=",middle,",value=",source[middle],"] is smaller than des, continue search from[",low,"to",high,"]" print "search complete, target element's index in source list is ",targetIndex
最后在分享一個(gè)
'fileName--BinarySearch.py'
src = [] def BinarySearch(low, high, target, *src): '二分查找' while low <= high: mid = (low + high) // 2 midVal = src[mid] if target < midVal: high = mid - 1 elif target > midVal: low = mid + 1 else: return mid BinarySearch(low, high, target, *src) print('Please input 10 number:') for number in range(10): src.append(int(input('Num %d:' % number))) sortList = tuple(src) key = int(input('Please input key:')) location = BinarySearch(0, len(src) - 1, key, *sortList) if location != None: print('Find target at %d' % (location + 1)) else: print('No target!')
實(shí)例補(bǔ)充
#!/usr/bin/python env # -*- coding:utf-8 -*- def half_search(array,target): low = 0 high = len(array) - 1 while low < high: mid = (low + high)/2 if array[mid] > target: high = mid - 1 elif array[mid] < target: low = mid + 1 elif array[mid] == target: print 'I find it! It is in the position of:',mid return mid else: print "please contact the coder!" return -1 if __name__ == "__main__": array = [1, 2, 2, 4, 4, 5]
運(yùn)行結(jié)果如下:
I find it! It is in the position of: 4 4 -1 I find it! It is in the position of: 0 0 -1
看完上述內(nèi)容,是不是對(duì)Python二分查找算法的實(shí)現(xiàn)方法有進(jìn)一步的了解,如果還想學(xué)習(xí)更多內(nèi)容,歡迎關(guān)注億速云行業(yè)資訊頻道。
免責(zé)聲明:本站發(fā)布的內(nèi)容(圖片、視頻和文字)以原創(chuàng)、轉(zhuǎn)載和分享為主,文章觀點(diǎn)不代表本網(wǎng)站立場(chǎng),如果涉及侵權(quán)請(qǐng)聯(lián)系站長(zhǎng)郵箱:is@yisu.com進(jìn)行舉報(bào),并提供相關(guān)證據(jù),一經(jīng)查實(shí),將立刻刪除涉嫌侵權(quán)內(nèi)容。