Re: [問題] 用遞迴做字串反轉..

[csihcs (非天夜翔)]

※ 引述《gs9706 (神手)》之銘言：
: 題目是這樣的....
: Write a recursive function to reverse a string by C.
: For example,   char a[ ] = "ABCDEFGH" ;
:                        printf (" %s \n", a);  /* "ABCDEFGH" */
:                        reverse_string (a);
:                        printf (" %s \n", a);  /* "HGFEDCBA" */
: 我怎麼想都想不出只傳一個位址參數的方法
: 又要遞迴.....
: 懇請解救~~~
int reverse_string(char *);

char str[] = "123456789";

     call time  | reserve c   call next
     str value  |
main:123456789  |
   a:123456789  |    1
   b:123456789  |    2
   c:123456789  |    3
   d:123456789  |    4
   e:123456789  |    5
   f:123456789  |    6
   g:123456789  |    7
   h:123456789  |    8
     return time|    back time   after copy  after put c return back
     str value  | c  str value
   i:123456789  |
   h:123456798  | 8  123456789    123456799  123456798
   g:123456987  | 7  123456798    123456988  123456987
   f:123459876  | 6  123456987    123459877  123459876
   e:123498765  | 5  123459876    123498766  123498765
   d:123987654  | 4  123498765    123987655  123987654
   c:129876543  | 3  123987654    129876544  129876543
   b:198765432  | 2  129876543    198765433  198765432
   a:987654321  | 1  198765432    987654322  987654321
main:987654321  |    987654321

--
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◆ From: 211.74.9.2
→ csihcs:if(!str || str[0] == '\0') return 0;
→ csihcs:else if(str[1] == '\0') return 1;
→ csihcs:... ; i = reverse_string(str); ... ; return i+1;
推 ledia:len = strlen(str); if(len <= 1) return;
→ ledia:swap(str[0], str[len-1]);
→ ledia:backup str[len-1]; str[len-1] = '\0';
→ ledia:reverse_string(str+1);
→ ledia:restore str[len-1];
→ ledia:好醜 ._.