将字符串中单词出现次序逆序。
对字符串扫描两次，第一次全体逆序，第二次以单词为单位逆序
/*
* "123 45 6" --->> "6 45 123"
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* reverse_string( char* p, unsigned int size )
{
char tmp;
unsigned int i;
if ( p == NULL || size == 0 || size == 1 )
return NULL;
i = size/2;
while ( i > 0 ) {
tmp = p[i];
p[i] = p[size-1-i];
p[size-1-i] = tmp;
i--;
}
return p;
}
int main( void )
{
char buf[100] = " 1234567 1 123 4 56 ";
unsigned int buf_size;
unsigned int i;
unsigned int j;
buf_size = strlen( buf );
printf("old string:\n%s\n", buf );
reverse_string( buf, buf_size );
printf("reversed first time:\n%s\n", buf );
i = 0;
while ( i < buf_size ) {
// skip spaces
while ( buf[i] == ' ' && buf[i] != '\0' ) {
i++;
}
j = i;
// find nearest space
while ( buf[i] != ' ' && buf[i] != '\0' ) {
i++;
}
// now j point to the first character of
// current word and i point to the nearest space
reverse_string( &buf[j], i-j );
}
printf("reversed string:\n%s\n", buf );
return 0;
}