博客

#include <stdio.h>

int strlen(char *src)
{
	int ret = 0;

	if(src == NULL){
		printf("args error\n");
		return -1; 
	}   
	
	while(src[ret])ret++;

	return ret;
}

void swap(char **p,char **q)
{
	while(*p < *q){
		**p ^= **q;
		**q ^= **p;
		**p ^= **q;
		
		(*p)++;
		(*q)--;	
	}
}

void swap1(char *p,char *q)
{
	while(p < q){
		*p ^= *q;
		*q ^= *p;
		*p ^= *q;
		
		p++;
		q--;	
	}
}


char *chang_word_position(char *p)
{
	char *a,*b,*tmp;

	if(p == NULL){
		printf("input args error\n");
		return NULL;
	}

	a = p;
	b = p + strlen(p) - 1;

	swap(&a,&b);
	//swap1(a,b);
	a = b = p;
#if 1	
	while(*tmp){
		while(*b != ' ' && *b) b++;
		//将b指针向后走，遇到空格或者'\0'停下
		tmp = b; 
		//将上述b以后的的位置赋值给tmp临时保存起来
		b--;
		//b向前移动一个字节
		swap(&a,&b);
		//将a b地址种的值进行位置交换
		
		while(*tmp == ' ')tmp++; 
		//如如果tmp在空格的位置，将tmp向后移动

		a = b = tmp;
		//将a b的指针赋值为tmp的位置
	}
#else	
	while(1){
		while(*b != ' ' && *b) b++;
		tmp = b;
		b--;
		swap(&a,&b);
		
		if(*tmp == '\0') break;

		while(*tmp == ' ')tmp++;

		a = b = tmp;
	}

#endif

}

#include <stdio.h>

int main(int argc, const char *argv[])
{
	char a[100] = {0};

	printf("please input string > ");
	scanf("%[^\n]",a);

	chang_word_position(a);

	printf("a = %s\n",a);
	return 0;
}