c中的Strlen错误

Question

 #include <stdio.h>
#include <time.h>
#include <string.h>
char* matrix [10][10];  
int main(void){         
        int i;
          char* list[4];
         char words[20][20]={" c a t "," c a r "," b e a r "," s h i p "," m o u s e "," b e a t l e "," c o a t "," n e s t "," i c e "," s u g a r "," b a c o n "," f r o w n "," s m i l e "," d e a d "," f e a t h e r "," g o a t "," h e n "," j e l l y "," k o a l a "," l i p s "};

        int length=0;
        int num;
        int k;
        int m;
        char otherString=0;
        char c;
        int j;
        int s;
        int r;


        char test[10];
        char* token;

const char *search = " ";
        char* empty="";
        int size;
        int ans;

        int x;
        int y;
        int pos;
        int pos2;
        int randRow;
        int randColumn;
        int chosen[10];
        int random;
        int d;
        int ROWS      = 10;      // number of rows
 int COLUMNS   = 10;      // number of columns




        printf("\tA\tB\tC\tD\tE\tF\tG\tH\tI\tJ\n");


        srand(time(NULL));


            for(r=0;r<10;r++){

            for(s=0;s<10;s++){
srand(time(NULL));

            c='1';  


        memset(matrix,c,sizeof(matrix));        
            }}


        for( i=0;i<4;i++){
    printf( "\n%d",i );
    d=0;
        do{
            random = (rand()%20);
            list[i]=words[random];
            d=0;
            for( j=0;j<i;j++){
                if(strcmp(words[random],list[j])==0)d=1;
            }
        }while(d);


    printf("%s",words[random]);
    token = strtok((words[random]),search); 
    printf("%s",token);
    while(token!=NULL) 
   {
      printf("\nrand%d",random);
      length=strlen(words[(random)]);
     printf("len is:%d",length);
      matrix [i][0]=token;
          for( k=1;k<=length;k++){
          token = strtok(NULL, search); 
        printf("%s",token);

            matrix [i][k]=token;

      } 
    } }


            for(r=0;r<10;r++){
            printf("\n");   
            for(s=0;s<10;s++){




                 printf("\t%c",matrix[r][s]);


            }}


        getchar();
            return 0;
            }

因为字符是用空格分隔的，所以 strlen 将其余的标记为

垃圾。所以答案总是2。有什么想法可以解决吗？长度是 总是 2。 也许它假设空格意味着字符串的结尾？？ 不知道怎么解决

Answer 1

除非您另有说明，否则 rand() 函数会自动播种值为 1。这就是为什么您每次都会得到相同的答案。

通过适当调用srand 进行修复，可能基于您的系统时钟时间。

strlen 不会丢弃空格，但会在到达第一个 \0 时返回。

Answer 2

问题来了：

token = strtok((words[random]),search); 

strtok 通过用 0 终止符替换分隔符来修改其参数；第一次调用strtok 后，" c a t " 变为" c"，长度为2。

您需要对words[random] 的副本 执行strtok 调用，如下所示：

char temp[20];
strcpy( temp, words[random] );
...
token = strtok( temp, search );

编辑

不要过分苛刻，但是......你的代码是一个一团糟。我不确定您要完成什么，但是您有大量未使用的变量、几种类型不匹配、您的输出令人困惑且难以阅读等。糟糕的格式使代码难以理解和遵循；只是使缩进一致暴露了几个问题（例如多余的srand 调用）。 gcc 抛出了一堆关于未使用变量的警告，以及缺少 srand 和 rand 的声明。

我已将您的代码缩减为专注于 strtok 和 strlen 问题，并重新格式化代码和输出以使其更具可读性。结果如下：

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

int main(void)
{
  int i;
  char words[20][20]={" c a t ",       " c a r ",     " b e a r ",   " s h i p ",   " m o u s e ",
                      " b e a t l e ", " c o a t ",   " n e s t ",   " i c e ",     " s u g a r ",
                      " b a c o n ",   " f r o w n ", " s m i l e ", " d e a d ",   " f e a t h e r ",
                      " g o a t ",     " h e n ",     " j e l l y ", " k o a l a ", " l i p s "};

  char* token;

  const char *search = " ";
  int random;

  srand(time(NULL));

  for( i=0;i<4;i++)
  {
    printf( "%d: ",i );
    random = rand() % 20;
    const char *blanks="                   ";
    printf("%.*s\"%s\", len is %2zu: token list:  ",(int) (strlen( blanks ) - (strlen(words[random]))),
                                                    blanks, words[random], strlen( words[random] ));
    char *sep = "";
    /**
     * strtok modifies the input string by overwriting the delimiter with
     * the 0 string terminator; to preserve the contents of words[random],
     * we need to copy it to a temporary string, and call strtok on that
     * copy.
     */
    char temp[20];                  
    strcpy( temp, words[random] );  
    token = strtok( temp, search ); 
    while(token!=NULL)              
    {
      printf("%s\"%s\"",sep, token);
      sep = ", ";
      token = strtok(NULL, search);
    }
    putchar( '\n' );
  }

  return 0;
}

这是输出：

0:             " c a r ", len is  7: token list:  "c", "a", "r"
1:       " b e a t l e ", len is 13: token list:  "b", "e", "a", "t", "l", "e"
2:           " b e a r ", len is  9: token list:  "b", "e", "a", "r"
3:             " c a t ", len is  7: token list:  "c", "a", "t"

我不知道你想用list 和matrix 完成什么，但这至少应该有助于解决你在标记字符串时遇到的任何问题。