1050 String Subtraction

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给定两个字符串S1和S2，程序的任务是计算S1减去S2的结果，即移除S1中所有出现在S2中的字符。代码通过创建一个unordered_set来存储S2中的字符，然后遍历S1，将不在集合中的字符添加到结果字符串中。最后输出结果。

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.

代码长度限制

16 KB

时间限制

100 ms

内存限制

64 MB

#include <iostream>
#include <unordered_set>
using namespace std;

int main() {
    string s1,s2;
    getline(cin,s1);
    getline(cin,s2);
    unordered_set<char> hash;
    for(auto item : s2){
        hash.insert(item);
    }
    string res;
    for(auto item : s1){
        if(!hash.count(item)) res += item;
    }
    cout << res << endl;
	return 0;
}