我有调用userInteractive（* anangramInfo）的函数，该函数传入struct anangramInfo的指针，并且此结构包含指向实际字谜的指针“ anagramPointer”。
所以，我从用户那里得到了标准输入。然后将其用作bsearch的关键字，以找到指针thoese anagram具有相同的anangram.sorted。然后将指针向左移动，直到键与anagram.sorted不匹配，然后将指针向右移至anagram.word，直到anagram.sorted不匹配。但这引起了我的细分问题
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include "anagrams.h"
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#define SIZE 80
//struct
struct anagram {
char word[SIZE];
char sorted[SIZE];
};
struct anagramInfo {
struct anagram *anagramPtr;
int numOfAnagrams;
};
/* qsort struct comparision function (product C-string field) */
int sortedMemberCompare( const void *ptr1, const void *ptr2 )
{
struct anagram *ia = (struct anagram *)ptr1;
struct anagram *ib = (struct anagram *)ptr2;
return strcmp(ia->sorted, ib->sorted);
/* strcmp functions works exactly as expected from
comparison function */
}
void userInteractive( struct anagramInfo *anagramInfoPtr ){
struct anagram a;
char data[SIZE];
char *pos;
printf("Enter a word to search for anagrams [^D to exit]:\n");
fgets(data, SIZE, stdin);
//get ripe of the '\n'
pos=strchr(data, '\n');
*pos = '\0';
strncpy(a.word,data,sizeof(data));
//lowercase word
int i;
for(i=0;data[i] != '\0';i++)
{
data[i]=(char)tolower(data[i]);
}
/* sort array using qsort functions */
qsort(data,strlen(data), 1, charCompare);
strncpy(a.sorted,data,sizeof(data));
//struct pointer to the elements
struct anagram *ptr= (struct anagram *)bsearch(a.sorted,anagramInfoPtr-> anagramPtr ->sorted,anagramInfoPtr-> numOfAnagrams,sizeof(struct anagram),sortedMemberCompare);
printf(ptr->word);
while(strncmp(ptr ->sorted,a.sorted,sizeof(a.sorted))==0) {
ptr--;
}
while(strncmp(ptr ->sorted,a.sorted,sizeof(a.sorted))==0) {
printf(ptr ->word);
printf(" ");
ptr++;
}
}
最佳答案
您的疏忽是bsearch不在连续数组上搜索；它甚至没有在正确的位置搜索，因为您正在搜索排序的字符串，但是您应该搜索字谜的排序成员：
struct anagram *ptr = (struct anagram *)bsearch(&a,
anagramInfoPtr-> anagramPtr,
anagramInfoPtr-> numOfAnagrams,
sizeof(struct anagram),
sortedMemberCompare);
然后，当
bsearch失败并返回NULL时，您无需检查ptr是否为NULL并使用它；因此，segfault。 （您也不要在Ctrl-D处选中NULL）。测试
这是一个修改后的版本-我添加了
charCompare函数，并用五个固定的字符串鞭打了main()，以便使其在工作后可以正常工作。#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#define SIZE 80
//struct
struct anagram {
char word[SIZE];
char sorted[SIZE];
};
struct anagramInfo {
struct anagram *anagramPtr;
int numOfAnagrams;
};
/* qsort struct comparision function (product C-string field) */
int sortedMemberCompare( const void *ptr1, const void *ptr2 )
{
struct anagram *ia = (struct anagram *)ptr1;
struct anagram *ib = (struct anagram *)ptr2;
return strcmp(ia->sorted, ib->sorted);
/* strcmp functions works exactly as expected from
comparison function */
}
int charCompare(const void *a, const void *b)
{
const char *aa = a, *bb = b;
if (*aa < *bb)
return -1;
if (*aa == *bb)
return 0;
return 1;
}
void userInteractive( struct anagramInfo *anagramInfoPtr ){
struct anagram a;
char data[SIZE];
char *pos;
printf("Enter a word to search for anagrams [^D to exit]:\n");
fgets(data, SIZE, stdin);
//get ripe of the '\n'
pos=strchr(data, '\n'); // In Windows this might be a "\r" maybe?
if (NULL == pos)
exit(0);
*pos = '\0';
strncpy(a.word,data,sizeof(data));
//lowercase word
int i;
for(i=0;data[i] != '\0';i++)
{
data[i]=(char)tolower(data[i]);
}
/* sort array using qsort functions */
qsort(data, strlen(data), 1, charCompare);
strncpy(a.sorted,data,sizeof(data));
//struct pointer to the elements
struct anagram *ptr = (struct anagram *)bsearch(&a,
anagramInfoPtr-> anagramPtr,
anagramInfoPtr-> numOfAnagrams,
sizeof(struct anagram),
sortedMemberCompare);
// You must check that ptr is not NULL.
if (NULL == ptr)
{
printf("Not found\n");
return;
}
printf("Found: %s\n", ptr->word);
/* Here there is a subtle error. If you find the FIRST item of the list,
this code will position itself BEFORE THE BEGINNING of the list, and
run a strncmp() against who knows what. Other segfault lurking! */
while(ptr > anagramInfoPtr -> anagramPtr && strncmp(ptr ->sorted,a.sorted,strlen(a.sorted))==0) {
ptr--;
}
// while(strncmp(ptr ->sorted,a.sorted,sizeof(a.sorted))==0) {
// ptr--;
//}
// Here too you should check you do not pass max number of anagrams,
// if you hit the last item of the lot.
while(strncmp(ptr ->sorted,a.sorted,sizeof(a.sorted))==0) {
printf(ptr ->word);
printf(" ");
ptr++;
}
}
int main()
{
int i;
struct anagramInfo *root;
root = malloc(sizeof(struct anagramInfo));
root->numOfAnagrams = 5;
root->anagramPtr = malloc(root->numOfAnagrams * sizeof(struct anagram));
strcpy(root->anagramPtr[0].word, "oriental");
strcpy(root->anagramPtr[1].word, "teaching");
strcpy(root->anagramPtr[2].word, "senator");
strcpy(root->anagramPtr[3].word, "admirer");
strcpy(root->anagramPtr[4].word, "rescued");
for (i = 0; i < root->numOfAnagrams; i++)
{
int j;
for (j = 0; root->anagramPtr[i].word[j]; j++)
root->anagramPtr[i].word[j] = tolower(root->anagramPtr[i].word[j]);
strcpy(root->anagramPtr[i].sorted, root->anagramPtr[i].word);
qsort(root->anagramPtr[i].sorted, strlen(root->anagramPtr[i].sorted), 1, charCompare);
}
qsort(root-> anagramPtr, root-> numOfAnagrams, sizeof(struct anagram), sortedMemberCompare);
for (;;)
userInteractive(root);
}
跑
$ gcc -W -Wall -o anagram anagram.c
$ ./anagram
Enter a word to search for anagrams [^D to exit]:
treason
Found: senator
Enter a word to search for anagrams [^D to exit]:
cheating
Found: teaching
Enter a word to search for anagrams [^D to exit]:
relation
Found: oriental
Enter a word to search for anagrams [^D to exit]:
$
关于c - C bsearch导致段错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13502202/