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.

我的解决方案

#include <iostream>
#include <string>
#include <set>
#include <cctype>

//解题思路:
//1.用string保存s1,set保存s2
//2.遍历s1,若s2中有,则不打印

using namespace std;

int main()
{
    string s1;
    set<char> s2;
    char c;
    
    getline(cin, s1);
    while ((c = cin.get()) != '\n') {
        s2.insert(c);
    }

    for (auto x : s1) {
        if (s2.find(x) == s2.end()) {
            cout << x;
        }
    }
    cout << endl;

    return 0;
}