#include<stdio.h>
#include<stdlib.h>
#include<string.h>
void generarDimension(int, void **, int);
void reallocarDimensiones(int, void **, int);
void preguntarValor(int *);
char *generarCadena(char *);
typedef struct listaAlu{//this is a list of students
char cedula[7];//this means id
char *nombreApellido;//this means name and lastname
short curso;//this means the year of the student in college/school
unsigned short anho;//and this means year-E.g: 2017
};
int main(void){
struct listaAlu *alu = NULL;
int salir=1;
char c;
unsigned int cont = 0;
unsigned int i;
size_t size = 0;
struct listaAlu *temp = NULL;
while(salir!=0){//Condition until user press exit option
printf("Agregar Alumno?Ingrese 1 para Agregar, y 0 para salir\n");//This means "Add student?Press 1 to add, and 0 to exit
preguntarValor(&salir);//this verifies user input
if(salir==1){//if user adds then it asks info of the student
cont++;
if ( NULL == ( temp = realloc ( alu, size + 2))) {//realloc for each character input and '\0'
fprintf ( stderr, "realloc problem\n");
}//this is for increasing the number of students
alu = temp;
printf("Ingrese Cedula:\n");//This means "Enter id"
scanf("%s", &(alu+(size))->cedula);
printf("Ingrese Nombre y Apellido:\n");//This means "Enter name and lastname"
(alu+(size))->nombreApellido = generarCadena((alu+(size))->nombreApellido);
printf("Ingrese Curso:\n");//This means enter college/school year
scanf("%hd", &(alu+(size))->curso);
printf("Ingrese Anho:\n");//and this means "Enter year"
scanf("%hd", &(alu+(size))->anho);
size++;
}
}
for(i=0;i<cont;i++){
printf("\tAlumno %d\n", i+1);
printf("Nombre:\t%s\n", (alu+i)->nombreApellido);
printf("Cedula:\t%s\n", (alu+i)->cedula);
printf("Curso:\t%d\n", (alu+i)->curso);
printf("Anho:\t%d\n", (alu+i)->anho);
}//This prints Everything the user entered
free(alu);
return 0;
}//Sorry for writing my program entirely on the main >.<
void generarDimension(int bloques, void **ptr, int tamanho){
void **ptrAux;
*ptrAux = malloc(bloques * tamanho);
if(*ptrAux==NULL){
printf("No se pudo almacenar memoria\n");
}else{
*ptr = *ptrAux;
free(ptrAux);
}
}//this I didn't use, but it is for generating an array through a pointer
void reallocarDimensiones(int bloques, void **ptr, int tamanho){
void **ptrAux;
*ptrAux = realloc(*ptr,bloques * tamanho);
if(*ptrAux==NULL){
printf("No se pudo almacenar memoria\n");
}else{
*ptr = *ptrAux;
free(ptrAux);
}
}//This I didn't either, but it is for reallocating any given pointer
void preguntarValor(int *n){
long entero, lector;
*n=-2;
do{
printf("\nSi ingresa otro numero o caracter, vuelva a ingresar opcion\n");
while(!scanf("%d", &entero)){
while((lector=getchar()) !='\n' && lector !=EOF );
}
*n=entero;
}while(*n>1 || *n<0);//You can change this parameters according to the numbers you want
}//This subrutine scans only integers between 1 and 0
char *generarCadena(char *scaneado){
char *temp = NULL;
int in = 0;
size_t size = 0;
while ( '\n' != ( in = getchar ( ))) {//loop until newline
if ( NULL == ( temp = realloc ( scaneado, size + 2))) {//realloc for each character input and '\0'
fprintf ( stderr, "realloc problem\n");
return scaneado;
}
scaneado = temp;
scaneado[size] = in;//set input
scaneado[size + 1] = '\0';//terminate
size++;
}
return scaneado;
}//This subrutine is for geting an input of chars of any given length
这是一个存储学院/学校学生名单的程序，我想知道如何改进这段代码，但是在我要求用户输入字符串的部分，在第二部分我无法输入任何东西。如果我尝试输入超过2名学生，我的代码不会打印我输入的学生的所有信息
答案 0 :(得分：0)
struct listaAlu *temp = NULL;
temp = realloc ( alu, size + 2);//<- wrong size
realloc(alu, size + 2)将在第一次运行中仅分配2个字节。但是你还需要更多。所需的总大小是数组中元素的数量乘以结构的大小。那是sizeof(struct listaAlu)，大约15个字节。
realloc( alu, sizeof(struct listaAlu) * (size + 1) );
您不需要将尺寸增加2。
确保检查正确位置的输入。 <{1}}失败时清除输入。
要获取名字和姓氏，您可以使用scanf和fgets
strdup和generarDimension存在重大问题。你可能想把它们留下来。
reallocarDimensiones<小时/> 的 修改
struct listaAlu{
char cedula[7];//this means id
char *nombreApellido;//this means name and lastname
short curso;//this means the year of the student in college/school
unsigned short anho;//and this means year-E.g: 2017
};
void clear()
{
int c;
while((c = getchar()) != '\n' && c != EOF);
}
int main(void)
{
struct listaAlu *alu = NULL;
size_t size = 0;
while(1)
{
alu = realloc( alu, sizeof(struct listaAlu) * (size + 1) );
if (!alu)
{
fprintf(stderr, "realloc problem\n");
break;
}
char buf[256] = { 0 };
printf("Enter id:\n");
fgets(buf, sizeof(buf), stdin);
buf[strcspn(buf, "\r\n")] = 0;
buf[sizeof(alu[size].cedula) - 1] = 0;
strcpy(alu[size].cedula, buf);
printf("Enter name and lastname:\n");
fgets(buf, sizeof(buf), stdin);
buf[strcspn(buf, "\r\n")] = 0;
alu[size].nombreApellido = _strdup(buf);
for(;;)
{
printf("Enter college/school year:\n");
if (scanf("%hd", &alu[size].curso) == 1)
break;
printf("input error\n");
clear();
}
for(;;)
{
printf("Enter year:\n");
if (scanf("%hd", &alu[size].anho) == 1)
break;
printf("input error\n");
clear();
}
size++;
printf("Press 1 to continue\n");
char input;
scanf(" %c", &input);
if(input != '1')
break;
clear();
}
for(size_t i = 0; i < size; i++)
{
printf("Alumno %d\n", i);
printf("Nombre:\t%s\n", alu[i].nombreApellido);
printf("Cedula:\t%s\n", alu[i].cedula);
printf("Curso:\t%hd\n", alu[i].curso);
printf("Anho:\t%hd\n", alu[i].anho);
}
for(size_t i = 0; i < size; i++)
free(alu[i].nombreApellido);
free(alu);
return 0;
}
不需要包含在不同的函数中。但出于有趣的目的，您可以执行以下操作：
realloc void* my_realloc1(void *ptr, int size)
{
ptr = realloc(ptr, size);
if (!ptr) printf("error\n");
return ptr;
}
//usage:
alu = my_realloc1(alu, sizeof(struct listaAlu) * (size + 1));
if (!alu) printf("error\n");
可以在这里工作，但无法获得任何结果。这只是额外的代码行。直接使用my_realloc1并执行必要的错误处理更容易，更清晰。
另一种方法是传递引用：
realloc这将再次起作用，但它只会添加更多代码。
函数void my_realloc2(void **ptr, int size)
{
*ptr = realloc(*ptr, size);
}
//usage: (*** Note the address `&` operator ***)
my_realloc2(&alu, sizeof(struct listaAlu) * (size + 1));
if (!alu) printf("error\n");
似乎没问题。您可以简化如下：
generarCadena并使用char *my_getline()
{
char *buf = NULL;
int in = 0;
size_t size = 0;
while('\n' != (in = getchar()))
{
size++;
buf = realloc(buf, size);
buf[size - 1] = (char)in;
}
size++;
buf = realloc(buf, size);
buf[size - 1] = 0;
return buf;
}
//usage:
printf("Enter name and lastname:\n");
alu[size].nombreApellido = my_getline();
来读取6个字符（因为scanf的大小为7）
cedula为安全起见，请确保输入为空终止，并清除缓冲区。
或者您可以像我在示例中使用的那样使用printf("Enter 6 characters:\n");
scanf("%6s", alu[size].cedula);
alu[size].cedula[6] = '\0';
clear();
。这最多可读取256个字符：
fgets char buf[256];
fgets(buf, sizeof(buf), stdin);
有时更容易，因为您不需要清除缓冲区。但fgets包含行尾字符buf，在这种情况下您必须删除\n。