c - 我需要知道一个字符串在另一个字符串中出现了多少次!使用C

Question

嗯，标题已经说明了我需要的内容。我尝试使用循环，但效果不佳，所以我来寻求你们的帮助!

这是我的代码:

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


int main()
{
    char word[31], word2[31];
    int size1, size2;
    int i, j, k; // control
    int count = 0;

        printf ("\nInput the first word");
        scanf ("%s", word);
        printf ("\nInput the second word: ");
        scanf (" %s", word2);

// I tried  to make  a loop through the first string and if it matches a letter, it would loop through the others (if they are equal, we have a substring), but failed to put it on the `for` loop


printf ("'%s' appears %d times within '%s'", word2, count, word);

return 0;
}

Answer 1

strstr是一个有用的函数，它大大缩短了您的代码；当您找到匹配项时，只需使用字符串的其余部分重试即可；

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

int main()
{
  const char* source = "aabaa";
  const char* string2find = "aa";

  int occurrences;
  const char *ptr, *lastfind = NULL;

  for(ptr=source; (lastfind=strstr(ptr, string2find)); ptr=lastfind+1)
    occurrences++;

  printf("%d\n", occurrences);

  return 0;
}

...或者，如果您确实决定不使用 string.h 函数来执行此操作，则代码会变得更加冗长；

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

int main()
{
  const char* source = "aaabaa";
  const char* string2find = "aa";

  int count=0;
  const char *position;
  for(position=source; *position; position++) {
      int comparepos, equal=1;
      for(comparepos=0; string2find[comparepos]; comparepos++) {
         if(position[comparepos] != string2find[comparepos]) {
             equal = 0;
             break;
         }
      }
      count+=equal;
  }

  printf("%d\n", count);

  return 0;
}