PAT Advanced 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 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.

这题考了差集，用unordered_map进行判别会节省一点时间

#include <iostream>
#include <unordered_map>
using namespace std;
unordered_map<char, bool> m;
int main() {
    string str, pattern, res;
    getline(cin, str);
    getline(cin, pattern);
    for(int i = 0; i < pattern.length(); i++) m[pattern[i]] = 1;
    for(int i = 0; i < str.length(); i++)
        if(!m[str[i]]) res += str[i];
    cout << res;
    system("pause");
    return 0;
}

PAT Advanced 1050 String Subtraction (20分)

原文：https://www.cnblogs.com/littlepage/p/12221187.html