1. 原題： https://www.patest.cn/contests/pat-a-PRactise/1050

2. 思路：

3. 源碼：

#include<iostream>using namespace std;int main(void){	//freopen("in.txt", "r", stdin);	char s1[10010], ch;	int s2[130] = { 0 };//存儲ascii的十進制	int i = 0, j = 0;	while ((ch = getchar()) != '/n')		s1[i++] = ch;	while ((ch = getchar()) != EOF)		s2[ch] = 1;//置為1	for (j = 0; j < i; j++)	{		if (s2[s1[j]] == 0)			printf("%c", s1[j]);	}	printf("/n");	return 0;}