PAT 1050 String Subtraction

#include<iostream>#include<string.h>//想用memset 在g++下要包这个头文件#include<string>using namespace std;int main(){string s1, s2,s3;getline(cin, s1);getline(cin, s2);char a[256];memset(a, -1, sizeof(a));for (int i = 0; i < s2.size(); ++i){if (a[s2[i]] < 0){a[s2[i]] = 1;}}for (int j = 0; j < s1.size(); j++){if (a[s1[j]] < 0){s3 += s1[j];}}cout << s3 << endl;return 0;}