替换字符串

题目要求把字符串S中所有A字串换成字串B

/*****

 *jimmy or kenthy i do not knwon!!!!

 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int get_next(char* t,int next[])
{
  int i = 0;
  int k = -1;
  int len = strlen(t);
  next[0] = k;
  
  while(i<len-1)
  {
   if( k==-1 || t[i]==t[k] )
     {
      k++;
      i++;
      if(t[i] != t[k])
        next[i] = k;
      else
        next[i] = next[k];
      }
    else
      k = next[k];
   }
}

int kmp_find(char* s,char* t)
{
  int i = 0;
  int j = 0;
  int len1 = strlen(s);
  int len2 = strlen(t);
  int next[len2];
  get_next(t,next);
  
  while(i<len1 && j<len2)
   {
     if( j==-1 || s[i] == t[j])
      {
       i++;
       j++;
      }
     else
      j = next[j];
   }
   
   if(j>=len2)
     return i-len2;
   else
   return -1;
}

char* substr(char* s,char* a,char* b)
{
    int len = strlen(a);
    
    int index = kmp_find(s,a);

    //kmp find where is a in s or you can use strstr
    char* head = s;
    *(head+index) = '\0';
    char* tail = s + index + len;

    //把字符串s分为  head a tail三部分
    sprintf(s,"%s%s%s",head,b,tail);
  
    if(kmp_find(s,a) != -1)//如果替换一个后还含有a继续
     return substr(s, a, b);
    else
     return s;
}
     
int main(int argc, char *argv[])
{
  char* s = (char*)malloc(100);
  memset(s,0,100);
  sprintf(s,"%s",argv[1]);
 
  printf("str:%s\n",s);
  printf("sub:%s by %s\nafter:%s\n",argv[2],argv[3],substr(s, argv[2], argv[3]));

  free(s);
  s=NULL;
  system("PAUSE");    
  return 0;
}


赠送shell实现

echo "xxxxxx" | sed 's/xxx/xxx/g'

awk -v str="sadsadas" 'BEGIN{gsub(/xxx/,"xxxxx",str);print str}'

vi ed等edit内直接s/xx/xxx/g

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