Question

我想用索引替换字符串。 x和y之间的字符串。如果要替换的字符串长度为y，则指针必须按差异递增。例如，

给出字符串([10 20]...[10 20]..[30 80]); x = 1（索引为[）和y = 7（索引为]），字符串替换为50，必须将其替换为{{1} }}。

我试过了：

(50...[10 20]..[30 80])

使用：

void replaceindex(char *s, char *replace, unsigned int start, unsigned int end)
{
  assert(start < end);

  char *p = s, *q = s, *r = replace;
  register unsigned int i =  0;
  int found = 0;

  while(*q) {

    if(found == 0 && i == start) {

      found = 1;

      for(; *r; ++r, ++start, ++q)
    *p ++ = *r;

      while(++start < end)
    q++;
    }

    *p ++ = *q ++;   
    i ++;
  }

}

输出结果为：

  char str[] = "([10 20]...[10 20]..[30 80])";
  printf("Before: %s\n", str);
  replaceindex(str, "50", 1, 7);
  printf("After: %s\n", str);

但我期待这个：

Before: ([10 20]...[10 20]..[30 80])
After: (500]...[10 20]..[30 80])0])

如何解决这个问题？

Answer 1

构建于the ideas from Anon ymous，但避免创建新字符串：

void replaceindex(char *s, char *replace, unsigned int start, unsigned int end)
{
  unsigned rl, sl;
  rl = strlen(replace);
  sl = strlen(s);
  ++end; /* change inclusive index to exclusive one */
  assert(start <= end);
  assert(rl <= end - start);
  memcpy(s + start, replace, rl);
  memmove(s + start + rl, s + end, sl - end + 1);
}

Answer 2

#include <stdio.h>
#include <string.h>
 char* replaceindex(char *s, char *replace, unsigned int start, unsigned int end)
 {

   char *rep= (char*)malloc(strlen(s)+1);
   memset(rep,0,strlen(s)+1);
   if(strlen(replace)<=(end-start))
     { memcpy(rep,s,start);
      memcpy(rep+start,replace,strlen(replace));
      memcpy(rep+start+strlen(replace),s+end,strlen(s+end));
      return rep;
    }
    else{free(rep);}
    return s;

 }


int main() {
char* z="This answer is crazy";
printf("%s",replaceindex(z,"Code",5,11));

return 0;
}

输出

This Code is crazy

编辑：

没有记忆： -

 #include <stdio.h>
#include <string.h>
void replaceindex(char *s, char *replace, unsigned int start, unsigned int end)
{
  if(strlen(replace)<=(end-start))
  {
  char* iter=  s+start+strlen(replace),*cursor=s+end;
  memcpy(s+start,replace,strlen(replace));
  while(*iter)
   *iter++=*cursor++;
  }
}


int main() 
{
char z[]="This answer is crazy";
replaceindex(z,"Code",5,11);
return printf("%s",z);
}

Answer 3

您需要两个修复：

       for(; *r; ++r, ++start, ++q)
     *p ++ = *r;

-      while(++start < end)
+      while(start++ <= end)
     q++;
     }

     *p ++ = *q ++;
     i ++;
   }
+  *p = '\0';

 }

第一个是因为你的结束指数是包容性的（从通话中判断），你想要先比较，然后再增加。第二种是终止新字符串。

请注意，如果strlen(replace) > end - start + 1，您将遇到严重问题。

用索引替换

3 个答案: