#include<stdio.h>
#include<cstring>
#include<vector>
using namespace std;
int main(){
char s[1101];
vector<char>a;
vector<char>::iterator it;
int i,p=0,j;
scanf("%s",s);
for(i=0;i<strlen(s);i++){
p=a.size();
for(it=a.begin();it<a.end();it++)
if(s[i]==*it)a.erase(it);
if(p==a.size())a.push_back(s[i]);
}
if(a.empty()){
printf("no");
return 0;
}
printf("%c",a[0]);
return 0;
}
样例全过,提交70分,用vector解