#include <stdio.h>
void dec_to_bin(char s[],int num){
    int a[100],m,i=0,j,k;
    while(1){
        m=num%2;
        a[i]=m;
        num=num/2;
        if(num==0)break;
        i++;
    }
    k=i;j=0;
        for(;j<=k;j++,i--){
            s[j]=a[i];
        }
}
int bin_to_dec(const char s[]){
  int i = 0, n = 0;
  while(s[i]!='\0'&&(s[i]=='0'||s[i]=='1')){
    n = n * 2 + (s[i] - '0');
    ++i;
  }
  return n;
}
main(){
    char string[100]={'\0'};
    int in_num,out_num;
   printf("输入一个十进制数:");
   scanf("%d",&in_num);
   dec_to_bin(string,in_num);
   printf("二进制是：%s\n",string);
   out_num=bin_to_dec(string);
   printf("十进制是：%d\n",out_num);
}