PAT 甲级 A1084 （2019/02/18）

#include<cstdio>
#include<cstring>
int main(){
    char str1[101], str2[101];
    bool HashTable[128] = {false};
    scanf("%s", str1);
    scanf("%s", str2);
    int len1 = strlen(str1);
    int len2 = strlen(str2);
    for(int i = 0; i < len1; i++){
        char ch1, ch2;
        int j;
        for(j = 0; j < len2; j++){
            ch1 = str1[i];
            ch2 = str2[j];
            if(ch1 >= 'a' && ch1 <= 'z')    ch1 -= 32;
            if(ch2 >= 'a' && ch2 <= 'z')    ch2 -= 32;
            if(ch1 == ch2)
                break;
        }
        if(j == len2 && HashTable[ch1] == false){
            printf("%c", ch1);
            HashTable[ch1] = true;
        }       
    }
    return 0; 
}