将字符串中的数字存储到动态内存中

    char str[] = "dsdlk2d4g5fhg5h4f4h65456gfh4fg6451";    //先计算出字符串中数字的个数    int count = 0;//存储数字的个数    int i = 0;  //  int *p = str;    while( str[i] != '\0') {        if (str[i] >= '0' && str[i] <= '9') {            count++;        }           i++;    }    printf("count =%d\n", count);    char *p = malloc(count + 1);    i = 0;    int k = 0;//用来标识别 数字数组元素的位置    while( str[i] != '\0') {        if (str[i] >= '0' && str[i] <= '9') {            *(p + k) = str[i];            k++;        }        i++;    }    *(p + k) = '\0';    printf("%s", p);    free(p);//释放堆区空间    p= NULL;//将指针变量指向一块无效的区域