Python实现Pat 1050. String Subtraction (20)

题目

Given two strings S1 and S2, S = S1 - S2 is defined to be the remaining string after taking all the characters in S2 from S1. Your task is simply to calculate S1 - S2 for any given strings. However, it might not be that simple to do it fast.

Input Specification:

Each input file contains one test case. Each case consists of two lines which gives S1 and S2, respectively. The string lengths of both strings are no more than 104. It is guaranteed that all the characters are visible ASCII codes and white space, and a new line character signals the end of a string.

Output Specification:

For each test case, print S1 - S2 in one line.

Sample Input:
They are students.
aeiou
Sample Output:
Thy r stdnts.

解答1，有时会超时

s1=input()s2=input()for c in s2:    s1=s1.replace(c,'')print (s1)

第一次提交，第四点超时了，第二次提交一样的代码就没超时了。

解答2，改变循环的对象，不超时了

s1=input()s2=input()sr=''for c in s1:    if c not in s2:        sr+=cprint (sr)