在C中对字符串列表数组进行排序

Question

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

void ascending_sort(char *name, char **pName, unsigned int size);

int main(){
   char * names[] = {"Ellin","Alexa","Eliza","Celiza", NULL};
ascending_sort(names[0],names,( sizeof(names)/sizeof(char *)) - 1);
return 0;
}

void ascending_sort(char *name, char **pName, unsigned int size){
    unsigned int i;
    unsigned int z;
    int keep;
    char temp;
    /// print out the array
    for (i = 0; i < size; i++)
    {
        printf("str: %s\n", pName[i]);
    }

    ///start sorting...
    for (i = 0; i < size; i++){
        keep = i;
        for(z = i; z < size; z++){
            if(pName[keep]>pName[z]){
               keep = z;
            }
        }
        temp = pName[i];
        pName[i] = pName[keep];
        pName[keep] = temp;

    }
    for (i = 0; i < size; i++){
        printf("str: %s\n", pName[i]);
    }
}

我对双指针（char**）感到困惑。 如何使用'for'循环打印出函数中数组的每个元素（以便我可以轻松理解）并对其进行排序（使用'for'循环）？

帮助修复我的排序算法，它不起作用

Answer 1

一个char **，是一个指向字符指针的指针。没有索引的数组名被视为指向数组中第一个元素的指针。您的数组是字符指针（指向其他地方内存中的字符串文字）。所以指向第一个元素的指针是指向字符指针的指针，或 char **。如下图，函数参数也可以指定为char *pnames[]，这样更好的体现了它是一个字符指针的数组（大小未知）。如果传递大小，则 for 循环最有意义。

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

void ascending_sort(char *name,char *pname[]);    
void ascending_sort2(char *name,char **pnames,unsigned int size);    

int main(){
   char *names[] = {"Dnames", "Bnames", "Anames", "Cnames", NULL};
   ascending_sort(names[0],names);
   ascending_sort2(names[0],names,( sizeof(names)/sizeof(char *)) - 1);
   ascending_sort2(names[0],names,(4));
return 0;
}

void ascending_sort(char *name,char *pname[]){
     //print out list of array
     // calculate array size
     unsigned int i = 0;
     char **ptemp = pname;
     while(*ptemp)  {
    i++;
        ptemp++;
     }
     unsigned int size = i;
     printf("------- 1 ----------\n");
     for (i = 0; i < size; i++)
     {
        printf("str: %s\n", pname[i]);  
     } 
     //start sorting...
}

void ascending_sort2(char *name,char **pnames, unsigned int size){
     //print out list of array
     unsigned int i,z;
     printf("------- 2 ---------\n");
     for (i = 0; i < size; i++)
     {
         printf("str: %s\n", pnames[i]);
     }
     //start bubble sorting...
     for( i = 0; i < (size - 1); i++)
     {
        for ( z = i; z < (size - 1); z++)
        {    
           if ( strcmp(pnames[z],pnames[z+1]) > 0 )
           {
              // swap the pointers
              char * temp = pnames[z+1];
              pnames[z+1] = pnames[z];
              pnames[z] = temp;
           }
        }
     }

     printf("--- after bubble sort: --------\n");
     for (i = 0; i < size; i++)
     {
         printf("str: %s\n", pnames[i]);
     }
}

Answer 2

使用 stdlib 中的 qsort 可能不是您想要的。但是下面的示例代码可能会清除 (char **) 指针的使用：

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

int compare (const void * ca, const void * cb)
{
    char **a = (char **)ca;
    char **b = (char **)cb;
    return strcmp(*a, *b);
} 

int main()
{
     int numnam, j;
     char *names[] = {"Ellin","Alexa","Eliza","Celiza"};
     numnam = sizeof(names)/sizeof(char *);
     qsort(names, numnam, sizeof(char *), compare);
     for (j = 0 ; j < numnam; j++)
         printf("%s \n", names[j]);
return 0;
}

Answer 3

固定 99.99%... !!

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

    void sort_name(char **pName, char order[], unsigned int size);

int main()
{ 
    char *names[] = {"Ellin","Alexa","Eliza","4-C", NULL};

    printf("[1] ");
    sort_name(names, "asc", (sizeof(names)/sizeof(char *))-1);

    return 0;
}

void sort_name(char **pName, char order[], unsigned int size){

     unsigned int i;
     unsigned int z;

     ///print out
     printf("Original list:\n\t");
     for (i = 0; i < size; i++)
     {
         (i<size-1) ? printf(" %s,", *(pName+i)) : printf(" %s\n", *(pName+i));
     }

     ///start sorting...
     if (!strcmp(order,"asc")){
            printf("    Ascending sorted list:\n\t");
     for (i=0; i <size; i++){
         for(z=i+1; z<size; z++){
             if(strcmp(*(pName+i),*(pName+z))>0){
                char *temp = *(pName+i);
                *(pName+i) = *(pName+z);
                *(pName+z) = temp;
             }
         }
     }
     for (i = 0; i < size; i++){
         (i<size-1) ? printf(" %s,", *(pName+i)) : printf(" %s\n", *(pName+i));
         }
     }

     else if (!strcmp(order,"desc")){
            printf("    Descending sorted list:\n\t");
     for (i=0; i <size; i++){
         for(z=i+1; z<size; z++){
             if(strcmp(*(pName+i),*(pName+z))<0){
                char *temp = *(pName+i);
                *(pName+i) = *(pName+z);
                *(pName+z) = temp;
             }
         }

     }
     for (i = 0; i < size; i++){
         (i<size-1) ? printf(" %s,", *(pName+i)) : printf(" %s\n", *(pName+i));
         }
     }

     else{
        printf(" That doesnt even make sense!");
     }
}