include <stdio.h>

include <ctype.h>

void word(char *p);
int main(void)
{
char a[81];
puts("input your string:");
gets_s(a,81);
word(a);
puts(a);

return 0;

}

void word(char p)
{
int begin,end;
for(begin=0; isspace( *(p+begin) ) ;begin++)
continue;
for(end=begin; !isspace( *(p+end) ) ;end++)
continue;
*(p+end) = '\0';
for(;(p+begin) != '\0';p++)
*p = *(p + begin);
*p='\0';
}

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最后一个for循环, 不应该是(p+begin) != '\0', 改成*(p+begin) != '\0'.

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楼上正解!!