将 char 数组中的单词转换为包含单个空格的行

Question

这个问题已经有答案了:

How do I concatenate the string elements of my array into a single string in C? (3 个回答)

已关闭 4 年前。

转换给定的char *input[]到一个带有单个空格的行

输入:

int n =3;
char *result;
char *input[]= {"one", "two", "three" };
result = convertToLine(n, input)

代码

char *convertToLine(int n, char *input[]) {
    int size = n* 2;
    char* string = (char*)malloc(sizeof(char)*size);        
    int i = 0;
    int k = 0;
    while (i <size){
        string[i] = *input[k];         
        string[i+1] = ' ';
        i++;
        k++;
     }
   string[n] = '\0';
   return string;
}

我的输出:空

预期输出:

result = "one two three"

Answer 1

您的代码中有几个错误

int size = n* 2; char* string = (char*)malloc(sizeof(char)*size);

所需的大小必须是最终大小，因此要合并更多空格和最终空字符的字符串长度之和。 n *2 只是字符串数量的两倍，这个不一样

string[i] = *input[k];

不会复制字符串，而只会复制其第一个字符

你可以这样做:

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

char *convertToLine(int n, char *input[]) {
  /* compute the needed size,
     of course can also use malloc then realloc to avoid that */
  int size = 0;
  int i;

  for (i = 0; i != n; ++i)
    size += strlen(input[i]) + 1;

  /* copy the strings */
  char * string = (char*)malloc(size); /* sizeof(char) is 1 by definition */
  char * p = string;

  for (i = 0; i != n; ++i) {
    strcpy(p, input[i]);
    p += strlen(p);
    *p++ = ' ';
  }
  p[-1] = 0;

  return string;
}


int main()
{
  char *input[]= {"one", "two", "three" };
  char * result = convertToLine(3, input);
  puts(result);

  free(result);
}

执行:

one two three

valgrind下执行:

pi@raspberrypi:/tmp $ valgrind ./a.out
==14749== Memcheck, a memory error detector
==14749== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==14749== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==14749== Command: ./a.out
==14749== 
one two three
==14749== 
==14749== HEAP SUMMARY:
==14749==     in use at exit: 0 bytes in 0 blocks
==14749==   total heap usage: 2 allocs, 2 frees, 1,038 bytes allocated
==14749== 
==14749== All heap blocks were freed -- no leaks are possible
==14749== 
==14749== For counts of detected and suppressed errors, rerun with: -v
==14749== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 3)