在字符串中找到最小和最长的单词

Question

我使用了：

保留用于记录单词的开始在哪里。

position_max和position_min用于记录最终字符单词的位置。

Max和min用于比较每个单词并找到最长和最小的长度。

lenght是整个字符串的长度。

#include<limits.h>
#include<stdio.h>
#include<time.h>
#include<math.h>
#include<string.h>
#include<conio.h>
#include<ctype.h>
#include<stdlib.h>
#include<malloc.h>


int main(void)
{
char *stringa = "alex keep all money";
size_t x;
int keep;       
int min;            
int max;        
int position_max;   
int position_min;   
int lenght;     
keep = 1;
max = 0;
min = INT_MAX;
position_max = 0;
lenght = strlen(stringa);
while(x != lenght + 1)
{
    if(isalnum(stringa[x]) != 0)
    {
        keep += 1;
    }
    
    if(isspace(stringa[x]) != 0 || stringa[x] == '\0')
    {
        if(keep > max)
        {
            position_max = x;
            max = keep;
        }
        if(keep < min)
        {
            position_min = x;
            min = keep;
        }
        keep = 0;
    }
    x++;
}
puts("the longest word:");
for(x = position_max - max; x != position_max; x++)
{
    printf("%c",stringa[x]);
}
puts("\n\nthe smallest word:");
for(x = position_min - min; x != position_min; x++)
{
    printf("%c", stringa[x]);
}
return 0;
}

Answer 1

正如其他人已经提到的那样 - 您有非初始化变量的问题（x，position_min），也错过了几个边缘案例：当您在开始/结束时有空格时连续的，这是固定版本：

int main(void) {
    const char * const stringa = " alex keep   all money ";
    size_t x = 0; // keep declaration and definition in one place, so it is easy to spot mistakes
    unsigned int keep = 0;
    unsigned int min = 0; // initial min/max should be zero to work properly later during printing
    unsigned int max = 0;
    size_t position_max = 0;
    size_t position_min = 0;
    const size_t length = strlen(stringa);
    
    while (x <= length) {
        if (x == length || isspace(stringa[x])) { // first cover end of string case
            if (keep > 0) { // multiple spaces
                if (max == 0 || keep > max) {
                    position_max = x;
                    max = keep;
                }
                if (min == 0 || keep < min) {
                    position_min = x;
                    min = keep;
                }
                keep = 0;
            }
        } else if (isalnum(stringa[x]))
            keep++;
        x++;
    }

    puts("the longest word:");
    for(x = position_max - max; x < position_max; x++) printf("%c", stringa[x]);
    puts("\n\nthe smallest word:");
    for(x = position_min - min; x < position_min; x++) printf("%c", stringa[x]);
    return 0;
}

Answer 2

该程序至少是因为在此中使用的变量X

while(x != lenght + 1)

并未初始化的

size_t x;

另一个问题是变量的初始化keep> keep by 1

keep = 1;

此可以结果可以结果对于像“ a a a a”这样的字符串，具有最大长度的子字符串将为“ a” a“，而不是“ bb”提供了最初的变量x 是由0初始化的，或者字符串从Space Cargue ''喜欢“ A” a“ a“），则最大substring将为> “”并使用表达式x = position_max -max在此循环中

for(x = position_max - max; x != position_max; x++)

再次导致不确定的行为。

另外，当字符串包含相邻的白色空间时，您必须考虑情况。

我将编写一个单独的函数，例如，如下演示程序所示。

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

struct SubString
{
    char *position;
    size_t length;
};

struct MinMax
{
    struct SubString min;
    struct SubString max;
};

struct MinMax minmax_string( const char *s, const char *delim )
{
    struct MinMax minmax = 
    { 
        .min = { .position = NULL, .length = 00 }, 
        .max = { .position = NULL, .length = 0 } 
    };

    for ( s += strspn( s, delim ); *s; s += strspn( s, delim )  )
    {
        const char *position = s;
        s += strcspn( s, delim );

        size_t length = s - position;

        if ( minmax.min.position == NULL )
        {
            minmax.min.position = ( char * )position;
            minmax.min.length = length;
            minmax.max.position = ( char * )position;
            minmax.max.length = length;
        }
        else if ( minmax.max.length < length )
        {
            minmax.max.position = ( char * )position;
            minmax.max.length = length;
        }
        else if ( length < minmax.min.length )
        {
            minmax.min.position = ( char * )position;
            minmax.min.length = length;
        }
    }

    return minmax;
}

int main(void) 
{
    const char *s = "alex keep all money";

    struct MinMax minmax = minmax_string( s, " \t" );

    printf( "The minimal string is \"%.*s\" at position %zu\n", 
        ( int )minmax.min.length, minmax.min.position, ( size_t )( minmax.min.position - s ) );
    printf( "The maximum string is \"%.*s\" at position %zu\n", 
        ( int )minmax.max.length, minmax.max.position, ( size_t )( minmax.max.position - s ) );
}

程序输出是

The minimal string is "all" at position 10
The maximum string is "money" at position 14

如果要使用标准C函数ISSPACE，那么函数minmax_string可以查看以下方式，

#include <stdio.h>
#include <ctype.h>

struct SubString
{
    char *position;
    size_t length;
};

struct MinMax
{
    struct SubString min;
    struct SubString max;
};

struct MinMax minmax_string( const char *s )
{
    struct MinMax minmax = 
    { 
        .min = { .position = NULL, .length = 00 }, 
        .max = { .position = NULL, .length = 0 } 
    };

    do
    {
        while ( isspace( ( unsigned char )*s )) ++s;

        if ( *s )
        {
            const char *position = s;

            while ( *s && !isspace( ( unsigned char )*s ) ) ++s;

            size_t length = s - position;

            if ( minmax.min.position == NULL )
            {
                minmax.min.position = ( char * )position;
                minmax.min.length = length;
                minmax.max.position = ( char * )position;
                minmax.max.length = length;
            }
            else if ( minmax.max.length < length )
            {
                minmax.max.position = ( char * )position;
                minmax.max.length = length;
            }
            else if ( length < minmax.min.length )
            {
                minmax.min.position = ( char * )position;
                minmax.min.length = length;
            }
        }
    } while ( *s );
    

    return minmax;
}

int main(void) 
{
    const char *s = "alex keep all money";

    struct MinMax minmax = minmax_string( s );

    printf( "The minimal string is \"%.*s\" at position %zu\n", 
        ( int )minmax.min.length, minmax.min.position, ( size_t )( minmax.min.position - s ) );
    printf( "The maximum string is \"%.*s\" at position %zu\n", 
        ( int )minmax.max.length, minmax.max.position, ( size_t )( minmax.max.position - s ) );
}

程序输出与上面显示的相同

The minimal string is "all" at position 10
The maximum string is "money" at position 14