char*s1, const char *s2，删除s1中s2出现过的字符_char* del_char( const char* s, char del ){

class Solution {
public:
    char* delChar(char* s1,char* s2)
    {
        if(s1==nullptr)
            return nullptr;
        if(s2==nullptr)
            retrun s1;
        
        const int tableSize=256;
        int table[tableSize];
        for(int i=0;i<tableSize;++i)
            table[i]=0;
 
        char* p=s2;
        while(*p != '\0')
        {
            table[*p]++;
            p++;
        }
 
        char* res=s1;
        char* ret=res;
        p=s1;
        while(*p != '\0')
        {
            if(table[*p]==0)
                *res++ = *p;
            p++;
        }
        *res='\0';
 
        return ret;
    }
}