#include "stdio.h"int main(){FILE *in,*out;char a1,a2,a3,b1,b2,b3;char a,b;in=fopen("未加密文件.txt","r");out=fopen("操作后文件.txt","w"); while((a=fgetc(in))!=EOF){a1=a/100;a3=a/10%10;a2=a%10;if((b=fgetc(in))==EOF)b1=3,b2=1,b3=0;else {b3=b/100;b1=b%10;b2=b/10%10;}fputc(a1+'0',out);fputc(b1+'0',out);fputc(a2+'0',out);fputc(b2+'0',out);fputc(a3+'0',out);fputc(b3+'0',out);}fclose(in);fclose(out);return 0;}=========================================================#include "stdio.h"int main(){FILE *in,*out;int over=0;int i;int t[6]={0};char a,b;in=fopen("未解密文件.txt","r");out=fopen("操作后文件.txt","w");while(!over){for(i=0;i<6;i++){t[i]=fgetc(in);if(t[i]==EOF){over=1;break;}t[i]-='0';}a=t[0]*100+t[4]*10+t[2];b=t[5]*100+t[3]*10+t[1];fputc(a,out);if(!over)fputc(b,out);}fclose(in);fclose(out); return 0;}