#include <iostream>
#include <string.h>
using namespace std;
int main()
{
char input[100];
int count[26];
int i=0,j=0,pos;
char ans[26];
memset(count,0,sizeof(count));
cin>>input;
while(input[i]!=‘\0‘)
{
pos=input[i]-‘a‘;
count[pos]++;
if(count[pos]==2)
ans[j++]=input[i];
i++;
}
ans[j]=‘\0‘;
for(i=0;i<strlen(ans);i++)
printf("%c",ans[i]);
}原文地址:http://mrcage.blog.51cto.com/6836193/1564416