程序代码：

#include<stdio.h>
#include <math.h>
char * fun(char *str,int *pint)
{
    char *p = str;
    int max = 0;
    char *pmax = NULL;
    int i = 0,j= 0,k = 0;
    while(*p)
    {
        if(' ' != *p)
        {
            i++;
        }
        else
        {
            if(i>max)
            {
                pmax = p-i;
                max = i;
                *pint = max;
                i = 0;
            }
        }
        p++;
    }
    return pmax;
}
void main()
{
    char a[] = "123  78974 561234567897 123456789";
    int n = 0;
    char *p = fun(a,&n);
    p[n] = '\0';
    printf("%s\n",p);
}