UVa 448 - OOPS!

Accepted date: 2013-03-27
Ranking (as of 2013-03-28): 34
Language: C++

/*
  UVa 448 - OOPS!

  To build using Visual Studio 2008:
    cl -EHsc -O2 UVa_448_OOPS.cpp
*/

#include <cstdio>
#include <cstring>
#include <cctype>
using namespace std;

const char* opcodes[] = {
  "ADD", "SUB", "MUL", "DIV", "MOV", "BREQ", "BRLE", "BRLS",
  "BRGE", "BRGR", "BRNE", "BR", "AND", "OR", "XOR", "NOT"
};

const int nr_operand_digits = 4;
const int nr_digits_max = 30 + nr_operand_digits - 1;
int idigits, nr_digits;
char digits[nr_digits_max + 1];

int get_opcode()
{
  if (idigits == nr_digits) {
    if (!gets(digits))
      return -1;
    idigits = 0;
    nr_digits = strlen(digits);
  }
  char c = digits[idigits++];
  if (isdigit(c))
    return c - '0';
  else
    return c - 'A' + 10;
}

int get_operand()
{
  if (idigits + nr_operand_digits > nr_digits) {
    memcpy(digits, digits + idigits, nr_digits - idigits);
    gets(digits + nr_digits - idigits);
    idigits = 0;
    nr_digits = strlen(digits);
  }
  int opr = 0;
  for (int i = 0; i < nr_operand_digits; i++, idigits++) {
    if (i)
      opr <<= 4;
    char c = digits[idigits];
    if (isdigit(c))
      opr += c - '0';
    else
      opr += c - 'A' + 10;
  }
  return opr;
}

void print_operand(int opr)
{
  int mode = (opr & 0xe000) >> 14, value = opr & 0x3fff;
  switch (mode) {
  case 0:
    printf("R%d", value); break;
  case 1:
    printf("$%d", value); break;
  case 2:
    printf("PC+%d", value); break;
  case 3:
    printf("%d", value); break;
  }
}

int main()
{
  int opc;
  while ((opc = get_opcode()) != -1) {
    printf("%s ", opcodes[opc]);
    print_operand(get_operand());
    if (opc <= 4 || opc >= 12 && opc <= 14) {
      putchar(',');
      print_operand(get_operand());
      if (opc >= 12 && opc <= 14) {
        putchar(',');
        print_operand(get_operand());
      }
    }
    putchar('\n');
  }
  return 0;
}