python常用算法题

一：

#计算平均数，中位数和众数

#coding:utf-8

#计算平均数，中位数和众数

import random

lst = [random.randint(0,10) for i in range(11)]

s = sum(lst)

length = len(lst)

average = s*1.0 / length

print "The average is:",average

lst.sort()
print "From small to bigger,",lst

middle = lst[length/2]
print "middle",middle

#众数 method1
m = {}
for i in lst:
    if i in m:
        m[i] +=1
    else:
        m[i] = 1
print m

max_number = max(m.values())
print max_number

for k,v in m.items():
    if v == max_number:
        print "mode is:",k

#众数method2
t = set(lst)
d = {}
for i in t:
    d[i] = lst.count(i)
print d
for k,v in m.items():
    if v == max_number:
        print "mode is:",k

二：

一列表由若干个整数组成，现要将偶数放到前面，奇数放在后面

#coding:utf-8
#一列表由若干个整数组成，现要将偶数放到前面，奇数放在后面
import random
lst = [random.randint(0,100) for i in range(90)]

print lst

odd = []
even = []
for i in lst:
    if i%2 ==0:
        even.append(i)
    else:
        odd.append(i)

print even
print odd

even.extend(odd)
print "result:",even

三：

列表中的字符串按照指定字符顺序排序

#coding:utf-8

#对列表中的字符串按照指定字符顺序排序

by_string = ["a","e","i","o","u"]
words = ["suzhou","shanghai","hangzhou","nanjing","beijing"]

result = {}
for word in words:
    n = []
    for i in word:
        if i in by_string:
            n.append(by_string.index(i))
        else:
            n.append(9)

        result[word] = n
print result
vs = result.values()
vs.sort()
print vs

sorted_word = []
for i in vs:
   for k,v in result.items():
       if v == i:
           sorted_word.append(k)

print sorted_word