A1050 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 10​^4​​. 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（字符串长度均小于10000），在第一个字符串中删去第二个字符串中出现过的所有字符并输出。

注意：

1. 熟练 string 类的使用

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
bool HashTable[128] = {false};
int main(){
  string a, b;
  getline(cin, a);
  getline(cin, b);
  int lenA = a.length();
  int lenB = b.length();
  for(int i = 0; i < lenB; i++){
    HashTable[b[i]] = true;
  }
  for(int i = 0; i < lenA; i++){
    if(HashTable[a[i]] == false)
      printf("%c", a[i]);
  }
  return 0;
}