C primer plus第12章課後習題9（理解指針與動態分配）

有兩個malloc和free，可看代碼//
///// 代碼不是原創，github下載的別人的。侵權刪

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define SIZE 40
char * * mal_ar(int n);
int main(void)
{
	int words, i;
	char * * st;

	printf("How many words do you wish to enter? ");
	scanf_s("%d", &words);
	getchar();					//濾掉回車
	printf("Enter %d words now:\n", words);
	st = mal_ar(words);
	printf("Here are your words:\n");
	for (i = 0; i < words; i++)
	{
		puts(st[i]);
		free(st[i]);	//釋放每個指針指向的內存
	}
	free(st);			//釋放指針數組

	return 0;
}

char * * mal_ar(int n)
{
	char * * pt;
	int i, j;
	char ch;

	//給n個指針分配動態內存空間，返回指針的指針
	pt = (char * *)malloc(n * sizeof(char *));
	for (i = 0; i < n; i++)
	{
		//給每個指針指向的地址分配內存空間
		pt[i] = (char *)malloc(SIZE * sizeof(char));
		//可以僅用scanf("%s", pt[i]);
		while (isspace(ch = getchar()))				//處理單詞之前的空格符
			continue;
		pt[i][0] = ch;								//單詞首字符
		j = 1;
		while (!isspace(pt[i][j] = getchar()))
			j++;
		pt[i][j] = '\0';							//將末尾的空格替換爲\0'
	}

	return pt;
}

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對理解指針和字符串的含義有意義
2020-04-10
大連

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