How to delete one of my "?->"?

I am writing a simple shell. I have posted my code here. This code works with the simple comments. But my problem now is everytime after I entered a commend, I have to hit enter key twice in order to get the output. Here is an example of my output

?-> ls
?->
a.out  getchar.cpp 

So my question is how to delete the second ?-> I would be so appreciate for your help. Thank you

//Shell
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <iostream>
#include <signal.h>
#include <string.h>

using namespace std;
#define ARGLENGTH  100
int execute(char *command[]);

int main()
{
    char *command[1000000];
    int numargs = 0;
    char buffer[ARGLENGTH];

    while(1) {
        printf("?-> ", numargs);
       if( fgets(buffer, ARGLENGTH, stdin) && *buffer != '\n' ) {
                 buffer[strlen(buffer)-1] = '\0';
                 command[numargs] = (char *)malloc(strlen(buffer)+1);
                 strcpy(command[numargs++], buffer);
        }
        else{
            if( numargs > 0 ){
                command[numargs] = NULL;
                execute(command);
                numargs = 0;
            }
        }
        if (command[0][0] == 'e'){
                break;}
        }
return 0;
}

int execute(char *command[])
{
    int pid,exitstatus;
    pid = fork();
    if( pid==-1 ){
            perror("fork failed");
            exit(1);
        }
    else if( pid==0 ){
           execvp(command[0], command);
            perror("execution failed");
            exit(1);
        }
        else {
                while (wait(&exitstatus) != pid);
        }
 }