How do I make a function that reads some values from console and then I return them? I mean not a single scanf
, multiple scanf
in another function and then return the values.
For example:
int main(){
write();
}
int write(void){
int a,b;
printf("Enter an int");
scanf("%d",&a);
printf("Enter another int");
scanf("%d",&b)
return a,b;
}
I know that C
is not C++
; I just want an example of C++
. Here is the full program that I made. I ask this question because I want to optimize my code. The above function I implemented in my program, but I didn't figure out to make it work, only with pointers.
#include <stdio.h>
#include <stdlib.h>
#define MAX 32
void read(int*x,int*y);
void write(int m[][MAX],int x,int y);
void display(int sir[][MAX],int x,int y);
int main(){
int x,y,m,n,a,b,i,k;
int matrice1[MAX][MAX]={0},matrice2[MAX][MAX]={0},result[MAX][MAX]={0},result2[MAX][MAX]={0};
read(&x,&y); //this is what i want to not use direct addreses if is possible
write(matrice1,x,y);
m=x;
n=y;
read(&x,&y);
write(matrice2,x,y);
system("cls");
printf("Prima matrice: \n");
for(i=0;i<m;i++){
for(k=0;k<n;k++){
printf(" %d",matrice1[i][k]);
}
printf("\n");
}
display(matrice1,m,n);
printf("\nA doua matrice: \n");
for(i=0;i<x;i++){
for(k=0;k<y;k++){
printf(" %d",matrice2[i][k]);
}
printf("\n");
}
display(matrice2,x,y);
printf("\nSuma matricelor: \n");
if(x>m){
a=x;
}
else
a=m;
if(y>n){
b=y;
}
else
b=n;
for(i=0;i<a;i++){
for(k=0;k<b;k++){
result[i][k]=matrice1[i][k]+matrice2[i][k];
printf(" %d",result[i][k]);
if(matrice1[i][k]%2!=0 && matrice2[i][k]%2!=0){
result2[i][k]=matrice1[i][k]+matrice2[i][k];
}
}
printf("\n");
}
printf("\nSuma matricelor impare<doar daca ambele sunt impare>: \n");
for(i=0;i<a;i++){
for(k=0;k<b;k++){
printf(" %d",result2[i][k]);
}
printf("\n");
}
return 0;
}
void write(int m[][MAX],int x,int y){
int i,k;
for(i=0;i<x;i++){
for(k=0;k<y;k++){
printf("elementul de pe linia %d, coloana %d: ",i,k);
scanf("%d",&m[i][k]);
}
}
}
void read(int*x,int*y){
printf("\nIntroduceti numarul de randuri a matricei: ");
scanf("%d",x);
printf("Introduceti numarul de coloane a matricei: ");
scanf("%d",y);
printf("\nIntroduceti elementele matricei.\n");
}
void display(int sir[][MAX],int x,int y){
int i,k;
for(i=0;i<x;i++){
for(k=0;k<y;k++){
if(sir[i][k]%2==0)
printf("numar par, pozitia %d,%d: %d\n",i,k,sir[i][k]);
}
}
}
Please note that C and C++ are different languages so the code will also be different.
For C, I'd suggest the following approach:
int readInts(int intArr[], size_t maxInts)
{
int i = 0;
while (i < maxInts && scanf("%d", &intArr[i]) == 1) { i++; }
return i;
}
Call it like this:
int myInts[100];
numInts = readInts(myInts, sizeof(myInts) / sizeof(myInts[0]);
In C++ one should avoid manual memory management whenever possible, therefore I'd do this:
std::vector<int> readInts()
{
int x;
std::vector<int> result;
while (std::cin >> x)
{
result.push_back(x);
}
return result;
}
Neither C nor C++ functions can return multiple values; not that it matters, since neither C nor C++ support multiple assignment either.
With C, you have the following choices:
void foo( int *arr, size_t arrSize ) { ... scanf( "%d", &arr[i] ); ... }
which would be called as: int values[N]; ... foo( values, N );
Alternately, you can have the function dynamically allocate a block of memory to hold its inputs, and return the pointer to that allocated block: /** * Stores inputs to a dynamically-allocated block of memory. * * Outputs: * * arrSize - Number of array elements allocated * arrCount - Number of array elements assigned */ int *foo( size_t *arrSize, size_t *arrCount ) { *arrSize = INITIAL_SIZE; // some size that covers most of your use cases *arrCount = 0; /** * Allocate the array */ int *arr = malloc( sizeof *arr * *arrSize ); if ( !arr ) // allocation failed, handle as appropriate int val; while ( scanf( "%d", &val ) == 1 ) { /** * If we've filled the array, extend it by doubling its size */ if ( *arrCount == *arrSize ) { int *tmp = realloc( arr, sizeof *arr * (*arrSize * 2) ); if ( tmp ) { arr = tmp; *arrSize *= 2; } else { // failed to extend the array, handle as appropriate } } arr[(*arrCount)++] = val; } return arr; }
which would be called as: size_t size = 0, count = 0; int *values = foo( &size, &count ); ... free( values ); // need to release the memory when you're done with it
Note that C functions cannot return objects of array type; that is, you can't do: int foo(void)[N] // illegal syntax { int arr[N]; ... return arr; }
Nor can you return a pointer corresponding to a local array, since the array ceases to exist once the function exits: int *foo( void ) { int arr[N]; ... return arr; // pointer will be invalid after function exits }
void foo( int *p1, double *p2 ) { ... scanf( "%d", p1 ); ... scanf( "%lf", p2 ); ... }
and call it as int bar; double bletch; ... foo( &bar, &bletch );
C++ gives you some different options:
std::vector<int> foo( void ) { std::vector<int> arr; size_t i = 0; ... std::cin >> arr[i++]; ... return arr; }
and call it as: std::vector<int> values = foo();
void foo( int& bar, double& bletch ) { ... std::cin >> bar; ... std::cin >> bletch; }
and call it as int x; double y; ... foo( x, y ); // no & operator since we're using references in the called function
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