理解指针&排序程序(c语言)

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strcpy的原理本身就是内容的复制,虽然参数均为地址.

直接,代码如下:

#include <stdio.h>#include <stdbool.h>#include <stdlib.h>#include <string.h>bool str_in(char **);void str_sort(char *[], int);void swap(void **p1,void **p2);void str_out(char *[], int);const size_t BUFFER_LEN = 256;const size_t NUM_P = 50;int main(void){//初始化char *pNum[NUM_P];int count = 0;//输入printf("请依次输入相关名称文段:\n");for( ; count < NUM_P; count++){if(!str_in(&pNum[count])){break;}}//排序str_sort(pNum,count);//输出str_out(pNum,count);/*供观察*/printf("%p %p %s\n",pNum,*pNum,*pNum);printf("%p %p %s\n",pNum,pNum[1],pNum[1]);printf("%p %p %s\n",pNum,*(pNum+1),*(pNum+1));printf("%p %p %s\n",pNum,*(pNum+2),*(pNum+2));return 0;}bool str_in(char **pString){char buffer[BUFFER_LEN];if(gets(buffer) == NULL){exit(1);}if(buffer[0] == '\0'){return false;}*pString = (char*)malloc(strlen(buffer) + 1);if(*pString == NULL){exit(1);}strcpy(*pString , buffer);printf("%p %p %s\n",pString,*pString,*pString);return true;}void str_sort(char *p[], int n){char *pTemp = NULL;bool sorted = false;while(!sorted){sorted = true;for( int i = 0; i < n-1; i++)if(strcmp(p[i],p[i+1]) > 0){sorted = false;swap(&p[i],&p[i+1]);}}}void swap(void** p1,void** p2){void *pt = *p1;*p1 = *p2;*p2 = pt;}void str_out(char *p[], int n){for( int i = 0; i < n; i++){printf("%s\n",p[i]);/*仅便于观察*///free(p[i]);//p[i] = NULL;}}

执行结果如下:

lnz@lnz:~/c_test$ ./a.out请依次输入相关名称文段:123450x7fff25caf920 0x23ce830 123451250x7fff25caf928 0x23ce850 1252350x7fff25caf930 0x23ce870 235170x7fff25caf938 0x23ce890 1712345125172350x7fff25caf920 0x23ce830 123450x7fff25caf920 0x23ce850 1250x7fff25caf920 0x23ce850 1250x7fff25caf920 0x23ce890 17lnz@lnz:~/c_test$

可见,静态分配在栈中,而动态分配在堆中;

并且这里排序交换的参数是指针数组的值,即文段的地址.

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