[英]Trying to pass ragged array to library qsort function
有什么辦法可以用破爛的數組嗎?
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
/*function for use in built-in quick sort*/
static int compare(const void *x,const void *y){
return strcmp(*(const char**)x, *(const char**)y);
}
int main(){
FILE *p = fopen("file.txt","w");
char ch = '\0',**c = (char**)calloc(6,sizeof(char*));
int n[6]={0},i=0,j=0;
fprintf(p,"jack\ndanny\njohn\nrachael\nrobin\ntom");
fclose(p);
p = fopen("file.txt","r");
while(1){/*count number of char to create ragged array*/
while((ch=getc(p))!= '\n'){
if(ch == EOF) break;
putchar(ch);
n[i]++;
}
printf(" %d\n",n[i]);
if(ch == EOF) break;
ch = '\0';
i++;
}
ch = '\0';
for(i=0;i<6;i++)/*allocating memory*/
c[i] = (char*) calloc(n[i],sizeof(char));
fclose(p);
i=0;
p = fopen("file.txt","r");
while(1){/*read from file to ragged array*/
while((ch=getc(p))!= '\n'){
if(ch == EOF) break;
*(c[i]+j) = ch;
j++;
}
i++;
j = 0;
if(ch == EOF) break;
ch = '\0';
}
/*using built-in quick sort*/
qsort(*c,6,sizeof(char*),compare);/*why won't this work?*/
for(i=0;i<6;i++)
printf("%s\n",*c[i]);
return 0;
}
for(i=0;i<6;i++)/*allocating memory*/
c[i] = (char*) calloc(n[i],sizeof(char));
您還需要在每個字符串之后考慮nul終止符,這應該是
c[i] = (char*) calloc(n[i] + 1,sizeof(char));
請記住,當您讀回字符串時,還需要確保它們也未終止。 現在不需要了,因為calloc()將確保字符串中的最后一個字節的值為0,但通常需要注意。
/*using built-in quick sort*/
qsort(*c,6,sizeof(char*),compare);/*why won't this work?*/
取消引用c並將其傳遞給qsort會是錯誤的,應該只是
qsort(c,6,sizeof(char*),compare);
與printf相同,* c [i]不是char *,這與printf%s格式化程序所期望的一樣。 它應該是
printf("%s\n",c[i]);
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