pku1049

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一道模拟题，利用状态机可以很容易的水过

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char code[257];/*指令*/
int pc;/*Program counter*/
int reg_a;/*寄存器a*/
int reg_b;/*寄存器b*/
int hex2dec(hex,length)
char *hex;//十六进制数

int length;//长度

{
     int res = 0;
     int i;
     for(i=0;i<length;i++){
     res *= 16;
     if(isdigit(hex[i])){
     res += hex[i] - '0';
     }
     else{
     res += hex[i] - 'A' + 10;
     }
     }
     return res;
}
void
dec2hex(h,a)
int h;
char *a;
{
     if(h<10) *a = h+'0';
     else *a = (h-10)+'A';
}
void
interpreter()
{
     int t;
     int end = 1;
     pc = 0;
     reg_a = 0;
     reg_b = 0;
     while(end){
     switch(code[pc]){
     case '0':
     reg_a = hex2dec(code+hex2dec(code+pc+1,2),1);
     pc += 3;
     break;
     case '1':
     dec2hex(reg_a,code+hex2dec(code+pc+1,2));
     pc += 3;
     break;
     case '2':
     t = reg_a;
     reg_a = reg_b;
     reg_b = t;
     pc++;
     break;
     case '3':
     t = reg_a + reg_b;
     reg_a = t&0xf;
     reg_b = ((t&0xf0)>>4);
     pc++;
     break;
     case '4':
     reg_a++;
     reg_a = reg_a&0xf;
     pc++;
     break;
     case '5':
     reg_a--;
     if(reg_a<0) reg_a += 16;
     pc++;
     break;
     case '6':
     if(reg_a) pc+=3;
     else{
         pc = hex2dec(code+pc+1,2);
     }
     break;
     case '7':
     pc = hex2dec(code + pc + 1,2);
     break;
     case '8':
     end = 0;
     break;
     }
     }
}
int main(){
     int i;
     while(scanf("%s",code)!=-1){
     if(code[0] == '8') break;
     interpreter();
     for(i=0;i<256;i++){
     if(code[i]) putchar(code[i]);
     else putchar('0');
     }
          putchar('\n');
     }
     return 0;
}