8-10.cpp

能判断二次函数是否有根

/*3208006411*/
#include<stdio.h>
#include<string.h>
void main()
{int alphabetic(char);
int longest(char[]);
int i;
char line[100];
printf("input one line:\n");
gets(line);
printf("The longest word is:");
for(i=longest(line);alphabetic(line[i]);i++)
printf("%c",line[i]);
printf("\n");
}
int alphabetic(char c)
{if((c>='a'&&c<='z')||(c>='A'&&c<='z'))
return(1);
else
return(0);
}
int longest(char string[])
{int len=0,i,length=0,flag=1,place=0,point;
for(i=0;i<=strlen(string);i++)
if(alphabetic(string[i]))
  if(flag)
  {point=1;
  flag=0;
  }
  else
   {flag=1;
    if(len>=length)
      {length=len;
       place=point;
       len=0;
       }
    }
  return(place);
  }