c - 句子倒转功能

Question

包含 stdio.h

包含标准库.h

包含string.h

#include <conio.h>

#define SIZE 40

int main( void )
{
    char str[ SIZE ];
    char strrev[ SIZE ];
    char *temp1;
    char *temp2;
    int turn = 0;

    printf( "Enter line of text: " );
    fgets( str, SIZE - 1, stdin );

    temp1 = strtok( str, " " );
    temp2 = strtok( NULL, " " );
    strcat( strrev, temp2 );
    strcat( strrev, temp1 );

问题是 while 里面的条件:

    while( temp1 != NULL && temp2 != NULL ){
           if( turn == 0 ){
               temp1 = strtok( NULL, " " );
               strcat( strrev, temp1 );
               strcat( strrev, temp2 );
               turn = 1;

               }//end if
           else{
                temp2 = strtok( NULL, " " );
                strcat( strrev,temp2 );
                strcat( strrev, temp1 );
                turn = 0;

                }//end else

           }//end while

    printf( "\nThe reversed sentence is: %s", strrev );

    getche();
    return 0;
}//end function main

既然字符串 temp1 或 temp2 最终都会得到一个 NULL，为什么循环不能正常运行？

Answer 1

可以用递归来反转句子，用sscanf来分割字符串:

#include <stdio.h>

void recursive(const char *s)
{
  char b[100];
  int n;

  if (sscanf(s, "%99s%n", b, &n) == 1)
    recursive(s + n), printf(" %s", b);
}

int main()
{
  recursive("foo bar baz");
  return 0;
}