动态内存分配

/*
   动态分配内存演示
   */
#include <stdio.h>
#include <stdlib.h>
int main() {
//int arr[5] = {1, 2, 3, 4, 5};
    /*for (num = 0;num <= 4;num++) {
printf("%d ", arr[num]);
}
printf("\n");*/
    int num = 0, size = 0;
    printf("请输入存储区个数：");
scanf("%d", &size);
int *p_num = (int*)malloc(size * sizeof(int));
if (p_num) {
for (num = 0;num <= size - 1;num++) {
*(p_num + num) = num + 1;
}
for (num = 0;num <= size - 1;num++) {
printf("%d ", *(p_num + num));
}
printf("\n");
free(p_num);
p_num = NULL;
}
return 0;
}





/*
   动态分配内存练习
   */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int *create(void) {
int num = 0;
int *p_num = (int*)malloc(7 * sizeof(int));
if (p_num) {
        for (num = 0;num <= 6;num++) {
   *(p_num + num) = rand() % 36 + 1;
   }
}
return p_num;
}
int main() {
int *p_num = NULL, num = 0;
srand(time(0));
    p_num = create();
if (p_num) {
   for (num = 0;num <= 6;num++) {
   printf("%d ", *(p_num + num));
   }
   printf("\n");
free(p_num);
p_num = NULL;
}
return 0;
}






/*
   动态分配内存练习
   */
#include <stdio.h>
#include <stdlib.h>
typedef struct {
int row, col;
} pixel;
/*pixel *read(void) {
pixel *p_pt = (pixel *)malloc(sizeof(pixel));
if (p_pt) {
printf("请输入点的位置：");
scanf("%d%d", &(p_pt->row), &(p_pt->col));
}
return p_pt;
}*/
void read(pixel **pp_pt) {
*pp_pt = (pixel *)malloc(sizeof(pixel));
if (*pp_pt) {
        printf("请输入点的位置：");
scanf("%d%d", &((*pp_pt)->row), &((*pp_pt)->col));
}
}
int main() {
    //pixel *p_pt = read();
pixel *p_pt = NULL;
read(&p_pt);
if (p_pt) {
   printf("点的位置是(%d, %d)\n", p_pt->row, p_pt->col);
free(p_pt);
p_pt = NULL;
}
return 0;
}








/*
   动态分配内存练习
   */
#include <stdio.h>
#include <stdlib.h>
char *read(void) {
    char *p_str = (char *)malloc(10 * sizeof(char));
if (p_str) {
printf("请输入字符串：");
fgets(p_str, 10, stdin);
}
return p_str;
}
void read1(char **pp_str) {
*pp_str = (char *)malloc(10 * sizeof(char));
if (*pp_str) {
printf("请输入字符串：");
fgets(*pp_str, 10, stdin);
}
}
int main() {
    //char *p_str = read();
char *p_str = NULL;
read1(&p_str);
if (p_str) {
printf("字符串是%s\n", p_str);
free(p_str);
p_str = NULL;
}
return 0;
}








/*
   动态分配内存作业
   */
#include <stdio.h>
#include <stdlib.h>
typedef struct {
int row, co;
} pixe;
pixe *midpt(const pixe *p_pt1, const pixe *p_pt2) {
    pixe *p_pt = (pixe *)malloc(sizeof(pixe));
if (p_pt) {
p_pt->row = (p_pt1->row + p_pt2->row) / 2;
p_pt->co = (p_pt1->co + p_pt2->co) / 2;
}
return p_pt;
}
void midpt1(const pixe *p_pt1, const pixe *p_pt2, pixe **pp_pt) {
*pp_pt = (pixe *)malloc(sizeof(pixe));
if (*pp_pt) {
(*pp_pt)->row = (p_pt1->row + p_pt2->row) / 2;
(*pp_pt)->co = (p_pt1->co + p_pt2->co) / 2;
}
}
int main() {
    pixe pt1 = {}, pt2 = {}, *p_pt = NULL;
printf("请输入一个点的位置：");
scanf("%d%d", &(pt1.row), &(pt1.co));
printf("请输入另外一个点的位置：");
scanf("%d%d", &(pt2.row), &(pt2.co));
//p_pt = midpt(&pt1, &pt2);
midpt1(&pt1, &pt2, &p_pt);
if (p_pt) {
printf("中间点位置是(%d, %d)\n", p_pt->row, p_pt->co);
free(p_pt);
p_pt = NULL;
}
return 0;
}










/*
   calloc演示
   */
#include <stdio.h>
#include <stdlib.h>
int main() {
    int *p_num = (int *)calloc(5, sizeof(int));
int num = 0;
if (p_num) {
        for (num = 0;num <= 4;num++) {
printf("%d ", *(p_num + num));
}
printf("\n");
free(p_num);
p_num = NULL;
}
return 0;
}