1050. String Subtraction (20)

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.

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给出两个字符串s和t，求s-t，即求s删去t中含有的字符得到的字符串。这里要注意输入要用getline，因为字符串可能含有空格。用一个数组记录t中有哪些字符，然后新建一个字符串res，用于储存结果，然后把含于s中但不含于t中的字符添加到res中，最后输出res。

代码：

#include <iostream>#include <cstring>#include <vector>#include <cstdlib>#include <cstdio>#include <set>using namespace std;int main(){    string s,t;    getline(cin,s);    getline(cin,t);    string res;    bool isvalid[1000];    memset(isvalid,true,1000);    for(int i=0;i<t.size();i++)    {        isvalid[int(t[i])]=false;    }    for(int i=0;i<s.size();i++)    {        if(isvalid[int(s[i])])        {            res+=s[i];        }    }    cout<<res;}