二分法查找(Python版)

#! /usr/bin/env python
# coding=utf-8
import random

def dichotomy(L,K,Index):
    if(len(L) == 1):
        return Index
    
    length = len(L) / 2
    hit = L[length]
    
    if(hit == K):
        return Index + length
    else:
        if hit > K:
            return dichotomy(L[:length],K,Index)
        else:
            return dichotomy(L[length + 1:],K,Index + length + 1)
        
    
    
if __name__ == '__main__':
    L = [random.randint(1,100) for i in range(1,20)]
    L = {}.fromkeys(L).keys()
    L.sort()
    
    K = random.choice(L)
    print L,K
    index = dichotomy(L,K,0)
    print index,L.index(K)