026.阿拉伯数字转换为罗马数字

#include <stdio.h>
#define ROWS 4
#define COLS 4
int nums[ROWS][COLS]={{1000,1000,1000,1000},
             {900,500,400,100},
             {90,50,40,10},
             {9,5,4,1}};
char *roms[ROWS][COLS]={{"m","m","m","m"},
                  {"cm","d","cd","c"},
                  {"xc","l","xl","x"},
                  {"ix","v","iv","i"}};
main(int argc,char *argv[ ])
{
  int low,high;
  char roman[25];
  if(argc<2)
  { printf("Usage:roman decimal_number\n");/*运行程序需带整数参数*/
    exit(0);
  }
  high=low=atoi(argv[1]);/*将第一个参数转换成整数*/
  checknum(low);
  if(argc>2)
  {/*带两个参数*/
  high=atoi(argv[2]);
  checknum(high);
  if(low>high)
    {
      low=high;
      high=atoi(argv[1]);
    }
  }
  else
    low=1;
  for(;low<=high;low++)
  {
    to_roman(low,roman);
    printf("%d\t%s\n",low,roman);
  }
}
checknum(int val)/*检查参数合理性*/
{
  if(val<1||val>9999)
  {
    printf("The number must be in range 1..9999.\n");
    exit(0);
  }
}
to_roman(int decimal,char roman[ ])/*将整数转换成罗马数字表示*/
{
  int power,index;
  roman[0]='\0';
  for(power=0;power<ROWS;power++)
    for(index=0;index<COLS;index++)
      while(decimal>=nums[power][index])
      {
        strcat(roman,roms[power][index]);
        decimal-=nums[power][index];
      }
}