PAT 1050 String Subtraction python解法

1050 String Subtraction （20 分）
Given two strings S_​1​​​ and S_​2​​​ , S=S​_​1​​​−S​_​2​​​ is defined to be the remaining string after taking all the characters in S​_​2​​​ from S​_​1​​​ . Your task is simply to calculate S_​1​​−S_​2​​ 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 S_​1​​​ and S​_​2​​​ , respectively. The string lengths of both strings are no more than 10^​4​​ . 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 S_​1​​​ −S​_​2​​​ in one line.

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

题意：对两个字符串 S_​1​​​和S​_​2做减法，结果是S_​1有而S_​2中没有的字符。

解题思路：对S_​1中每个元素，如果该元素不在S_​2中，则输出。

s1 = input()
s2 = input()
#s1 = 'They are students.'
#s2 = 'aeiou'
for i in s1:
    if i not in s2:
        print(i,end='')