输出最长的单词

输入一行字符，输出最长的单词。

#include<stdio.h>
#include<string.h>
#define N 100
int LongestVoc(char str[]);
int Alpha(char c);
int main(void){
    char str[N];

printf("please input a string:");
    gets(str);
    int pos=LongestVoc(str);
    printf("result is ");
   for(int i=pos;Alpha(str[i]);i++)
    printf("%c",str[i]);
}
int Alpha(char c){
    if((c>='a'&&c<='z')||(c>='A'&&c<='Z'))
        return 1;

    else return 0;
}
int LongestVoc(char str[]){
    int len=0,length=0,flag=1,place=0,point;
    //flag=0 not a new vocabulary flag=1 is a new vocabulary.
    for(int i=0;i<strlen(str);i++){
        if(Alpha(str[i])){
            if(flag){
                point=i;
                flag=0;
            }
            else{
                len++;
            }

        }else{
            flag=1;
            if(len>=length){
                length=len;
                place=point;
                len=0;
            }
        }
    }
        return place;



}