1050 String Subtraction

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 1. 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：

　　给出两个字符串，提出第一个字符串中，两个字符串都出现的字符。

思路：

　　模拟。

Code：

#include <bits/stdc++.h>

using namespace std;

int main() {
    string s1, s2;
    getline(cin, s1);
    getline(cin, s2);
    unordered_set<char> visited;
    for (int i = 0; i < s2.length(); ++i) visited.insert(s2[i]);
    string ans = "";
    for (int i = 0; i < s1.length(); ++i)
        if (visited.find(s1[i]) == visited.end()) ans += s1[i];
    cout << ans << endl;
    return 0;
}