Sum of two arrays
The exercise says "Make a function with parameters two int arrays and k which is their size. The function should return another array (size k) where every element of it is the sum of the two arrays of the same position. That's what I wrote, but it crashes. Do I have to do it with pointers?
#include <stdio.h>
#include <stdlib.h>
void sumarray(int k,int A[k],int B[k]){
int sum[k],i;
for(i=0;i<k;i++){
sum[i]=A[i]+B[i];
printf("sum[%d]=%d\n",i,sum[开发者_C百科i]);}
}
main(){
int i,g,a[g],b[g];
printf("Give size of both arrays: ");
scanf("%d",&g);
for(i=0;i<g;i++){
a[i]=rand();
b[i]=rand();
}
sumarray(g,a,b);
system("pause");
}
Example: If i have A={1,2,3,4} and B={4,3,2,1} the program will return C={5,5,5,5).
This:
int i,g,a[g],b[g];
causes undefined behaviour. The value of g
is undefined upon initialisation, so therefore the length of a
and b
will be undefined.
You probably want something like:
int i, g;
int *a;
int *b; // Note: recommend declaring on separate lines, to avoid issues
scanf("%d", &g);
a = malloc(sizeof(*a) * g);
b = malloc(sizeof(*b) * g);
...
free(a);
free(b);
Its impossible to first do a[g]
when dynamically getting g
.
Your first lines in main should be:
int i,g;
int *a,*b;
printf("Give size of both arrays: ");
scanf("%d",&g);
a = (int *)malloc(g*sizeof(int));
b = (int *)malloc(g*sizeof(int));
int sum[k] ;
k
is a variable but the size of the array should be a constant.
The function should return another array (size k) ...
But the function you wrote returns void
which is clearly wrong.
Do I have to do it with pointers?
Yes.
One issue is that you've attempted to declare dynamically sized arrays on the stack (e.g. a[g]
). You need to declare pointers for each array and then dynamically allocate your variable sized array once you've read in the value of g
.
change the function summary signature (the definition part of the declaration) to this and try it out:
void sumarray(int k,int* A,int* B){
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