1.归并排序 L1 = [1, 2, 4, 6, 9]L2 = [2, 3, 5, 7, 8]L3 = []for x in L1: while len(L2) > 0: if x
1.归并排序
L1 = [1, 2, 4, 6, 9]L2 = [2, 3, 5, 7, 8]L3 = []for x in L1: while len(L2) > 0: if x > L2[0]: L3.append(L2.pop(0)) else: L3.append(x) break if len(L2) == 0: L3.append(x) L3.extend(L2)print(L3)
2.按单词反转字符串
s = 'I Love You'tmp = s.split()s2 = ' '.join(tmp[::-1])print(s2)
3.找出列表不重复元素并按原来的顺序
lst = [1, 2, 1, 3, 1, 2, 5]lst2 = []lst3 = []tmp = []# count方法for i in lst: if lst.count(i) > 1: # 删除所有i元素 pass else: lst2.append(i)print(lst2)# in方法for x in lst: if x not in tmp: lst3.append(x) tmp.append(x) else: if x in lst3: lst3.remove(x) print(lst3)
4.查找一个列表中的最大值
lst = [1, 2, 1, 3, 2, 5,4]if len(lst) == 0: print('List is null.')else: max = lst[0] for i in lst: if i > max: max = i print(max)
5.字符串转化为数字
# 传统s = '-123.12345'x = 0 # resultsign = 0 # sign of .loc = 0 # location neg = 0 # sign of negativenum = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.', '-']i = 0n = 0m = 0for i in s: if i in num: if num.index(i) == 10: sign = 1 elif num.index(i) == 11: neg = 1 else: if sign: loc +=1 x = x + num.index(i) * (0.1 ** loc) else: x = x * 10 + num.index(i)if neg: x *= -1print(x)# pythons2 = '-1234.123'result = 0mloc = 0integers, *decimals = s2.split('.')*nega, integer = integers.partition('-')if len(decimals) == 0: decimal = '0'else: decimal = decimals[0]for n in integer: result = result * 10 + num.index(n)for m in decimal: mloc += 1 result = result + num.index(m) * (0.1 **mloc)if len(nega) == 2: result *= -1print(result)
PS:
partition ==> rpartition
6.不适用组合数打印杨辉三角
lst = []for n in range(1,11): # 从第1行开始，n就是第几行 if n == 1: lst.append([1]) elif n == 2: lst.append([1, 1]) else: sub_lst = [1] for k in range(1, n-1): # 从第0列开始，k从第1列到n-1 sub_lst.append(lst[n-2][k-1] + lst[n-2][k]) sub_lst.append(1) lst.append(sub_lst) # 增加第n行的列表 for s in lst: print(' '.join(str(x) for x in s))
7.四则运算的括号匹配
exp = '3 * {3 +[(2 -3) * (4+5)]}'brackets = ( ('(', ')'), ('[', ']'), ('{', '}'))stack = []for c in exp: if c in (t[0] for t in brackets): stack.append(c) elif c in (t[1] for t in brackets): if len(stack) == 0: print('1.error,no enough left brackets {}'.format(c)) break left = [t[0] for t in brackets if c == t[1]] if stack.pop() != left[0]: print('2.error,no enough right brackets {}'.format(c)) breakelse: if len(stack) == 0: print('ok') else: print('3.error, unnecessary brackets {}'.format(stack))8.不带括号的四则运算转化为前缀表达式
exp = '2 * 3 + 1 - 4 / 2 * 7 - 1' # 6 +1 - 14 -1 => -8symbols = {'+': 0, '-': 0, '*': 1, '/': 1}exp = exp.split()stack = []for item in exp: if item not in symbols.keys(): # 数字直接入栈 stack.append(item) else: while len(stack) > 1 and symbols[stack[-2]] >= symbols[item]: # 栈内有元素，且栈内上层符号优先级大于等于入栈符号 r = stack.pop() s = stack.pop() l = stack.pop() t = {'root':s, 'left':l, 'right':r} #取出上三个，做树 stack.append(t) # 入栈 stack.append(item) #第一个入栈符号，直接入栈|已经做树，入栈# 继续做树while len(stack) > 2: r = stack.pop() s = stack.pop() l = stack.pop() t = {'root':s, 'left':l, 'right':r} stack.append(t) ret = stack.pop()import pprintpprint.pprint(ret)
