Contest Clarifications

为什么老超时呢？？？？
#include "stdio.h"
int main()
{
    int i, sum, k = 1;
    char c;
    i = sum = 0;
    while(scanf("%c", &c))
    {
        if(c >= 65 && c <= 90)
    {
      i ++;
      if(c == 'A')
        sum += 4;
      else if(c == 'B')
        sum += 3;
      else if(c == 'C')
        sum += 2;
      else if(c == 'D')
        sum += 1;
      else if(c == 'F')
        sum += 0;
      else if(c == 'E' || c >= 71)
        k = 0;             
    }
    else if(c == '\n')
    {
      if(k == 0)
      {
        printf("Unknown letter grade in input\n");
                k = 1;
      }
      else
          printf("%.2lf\n", 1.0*sum / i);
         sum = 0;
      i = 0; 
    }
    }
    return 0;
}
德成 at 2009-07-25 15:00:38

RE:为什么老超时呢？？？？
while(scanf("%c", &c)!=EOF)
xiangsicao at 2009-07-25 15:55:59