Question

处理二进制搜索。下面的代码应该解释我正在尝试做什么。用户输入一个单词，然后实现二进制搜索以搜索单词表。问题是二进制搜索。它正在运行，但即使我知道它在那里，它也没有在wordlist中找到这个词。我知道代码可能更好但它应该工作。有人放光了吗？

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


char dictionary[400000][45];

int main(void)
{
FILE infile;
int i=0;
int num;
int index;
char buffer[45];
char userword[45];

fp1 = fopen("C:/Users/Aaron/ProgrammingAssignment/dictionary.txt","rb");

    if (fp1 == NULL)
    {
    printf("The dictionary file did not open\n");
    exit(0);
    }

    else
    {
    printf("Dictionary file is open\n");
    }

    while(fgets(buffer,45, fp1)!=NULL)
        {
            strcpy(wordlist[i],buffer);
            //printf("Line %d: %s",i,wordlist[i]);
            i++;
        }

    printf("Your wordlist is now in the dictionary array");

    do
    {
    //fscanf(fp2,"%s", userword);
    printf("Enter a word to be spell checked: ");
    fgets(userword, 43, stdin);

    //and do a binary search
    index = BinarySearch(userword,0,i);
    if(index > -1)
        printf("%s was found in the wordlist", userword);
    else
        printf("%s was not found in the dictionary", wordcheck);
    }
    while(wordlist != NULL);

    if(index>-1) //The word was found
   {
      printf("That is correctly spelled\n");
   }
   else 
   {
      printf("That word is spelt wrong\n");
   }


return 0;
}

int BinarySearch(const char userword[],int left,int right)
  { int high = 400000;   
    int low = 0; 
    int target; 
    int count = 0;

    while (high >= low)   
      { target = low + ((high - low) / 2);

        // show tries for demonstration only
        printf("%d, ",target);

        if (strcmp(userword, wordlist[target]) < 0)
          high = target -1;
        else if (strcmp(userword, wordlist[target]) > 0)
          low = target + 1;
        else 
        return target;
      }
    return -1; 
  }

Answer 1

您的二进制搜索功能忽略了传入的值left和right。

不应该。

它可能应该开始：

int BinarySearch(const char userword[], int left, int right)
{
    int high = right;   
    int low = left;

阅读完毕后，您应该关闭字典。

您需要考虑right是最后一个有效元素的索引还是'最后一个元素的索引后面的索引'。这可能意味着您需要在对函数的调用中传递i - 1。

您应该考虑调用strcmp()一次并捕获其返回值;它相对昂贵：

int rc = strcmp(userword, wordlist[target]);

if (rc == 0)
    return target;
else if (rc < 0)
     high = target - 1;
else
     low = target - 1;

搜索不工作需要一些建议

1 个答案: