Question

我需要二进制搜索数组的帮助，我的问题是我觉得我有所有正确的要求但它根本没有搜索。我没有收到任何错误消息。只是没有得到我想要的结果。数组是全局初始化的，也是最大字数。这就是我的功能：

int wordsFindFast(const char const* w){
/*
    ROLE            Determines whether a given word is in our words array
                    Implements fast binary search algorithm
    PARAMETERS      w   word to look for in the words array
    RETURN VALUE    1   true if the word was found
                    0   false if the word was not found
*/

int first, middle, last;

first = 0;
last = (MAX_NB_WORDS) - 1;
middle = (first+last)/2;

while(first <= last)
{
    if (words[middle] < w){
        first = middle + 1;
    }//end if
    else if(words[middle] == w){
        return 1;
    }//end else if
    else
        last = middle - 1;
        middle = (first + last)/2;
}//end while

return 0;
}

Answer 1

你无法比较c中的字符串

if (words[middle] < w)

使用strcmp()，

while(first <= last)
{
    if (strcmp(words[middle],w)==0)
    {
         return 1;

    }
   else if(strcmp(words[middle], w)<0)
    {
        first=middle+1;
    } 
    else
        last = middle - 1;
  middle = (first + last)/2;
}//end while

Answer 2

您无法比较C中的字符串。您应该使用标头strcmp中声明的标准库函数string.h逐个字符地比较它们。另外，请注意

const char const *w

函数wordsFindFast的参数列表中的

与

相同

const char *w

这意味着w是指向char类型的对象的指针，该对象是常量，即是只读的。您应该将功能更改为 -

int wordsFindFast(const char *w) {
    int first = 0;  
    int last = MAX_NB_WORDS;
    int middle;

    int cmpval;

    while(first <= last) {
        middle = (first + last) / 2
        cmpval = strcmp(w, words[middle]);
        if(cmpval == 0)
            return 1;
        else if(cmpval < 0)
            last = middle - 1;
        else
            first = middle + 1;
    }
    return 0;
}

二进制搜索字符串数组

2 个答案: