参考回答：
int main(){char buffer[80]="AaABbBcBbcvQv";for(int i=0;buffer[i]!=' ';i++){if(buffer[i+2]==' '){printf("ok");printf("%cn",buffer[i]);return 0;}if(buffer[i]==buffer[i+2] && buffer[i]!=buffer[i+1]){int j=i;while(buffer[j+3]!=' '){buffer[j]=buffer[j+3];j++;}buffer[(j+2)]=' ';if((i-1)>0){i=i-1;}}printf("%cn",buffer[i]);}return 0;}
