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Why does this function incorrectly multiply the values ​​in the array by the given number?

I am trying to write a function in C that takes a pointer to an array and returns that pointer with all the values ​​multiplied by multiple. I have:

int* returnNpledArray(int *a, int n){
    int i = 0;

    for(i = 0; i < SIZE; i++){
        *a++ *= n;
    }
    return a;
}

but when I call it, what I do is basically like this:

    int sample2[] = {-10,-8,-6,-4,-2,0,2,4,6,8};
    returnNpledArray(sample2, 3);

    int d = 0;
    for (d = 0; d < SIZE; d++){
        printf("%d\n", *sample2); 
    }

the whole array prints as soon as the first value in it, multiplied by n. I thought that since in the function I say * a ++ * = n; that I am both dereferencing the value at that location in AND, incrementing the pointer. How can I get this to work?

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6 answers


You should do the following for loop:

for (d = 0; d < SIZE; d++){
    printf("%d\n", *(sample2 + d));
}


OR

for (d = 0; d < SIZE; d++){
    printf("%d\n", sample2[d]);
}
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Since you are stuck at one pointer i.e. sample

by doing printf("%d\n", *sample2);

, instead it should beprintf("%d\n", sample2[d]);



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If you only want to iterate with pointers, you can use the following:

int *current = sample;
int *end = sample + SIZE;
for ( ; current < end; current ++) {
    printf("%d\n", *current); 
}

Note that we are advancing the pointer current

here to point to the next one int

; Also, it end

is a pointer that only points to the last element in the array sample

.

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As mentioned above, you just print the first value

#include<iostream>
using namespace std;

#define SIZE 10
int* returnNpledArray(int *a, int n){
    int i = 0;

    for(i = 0; i < SIZE; i++){
        *a++ *= n;
    }
    return a;
}

int main()
{
int sample2[] = {-10,-8,-6,-4,-2,0,2,4,6,8};
returnNpledArray(sample2, 3);

int d = 0;
for (d = 0; d < SIZE; d++){
    printf("%d\n", sample2[d]);
}
}

Output

-30
-24
-18
-12
-6
0
6
12
18
24
Program ended with exit code: 0
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The typical way to write code would be a[i] *= n;

. You also neglected to point out where it is SIZE

defined, which could be a bug.

Be that as it may, the increment has to happen, return the pre-incremented value, play out, read, modify, write. The multiplication code should work.

Ultimately, it really is your fault printing function. It is not a repetition of an array. Tryprintf("%d\n", sample2[d]);

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Why are you making it difficult when multiplying? I think you can do it like this.

int* returnNpledArray(int *a, int n){
    int i = 0;

    for(i = 0; i < SIZE; i++){
        a[i] = a[i]*n;
    }
    return a;
}

Here is the main function

int sample2[] = {-10,-8,-6,-4,-2,0,2,4,6,8};
returnNpledArray(sample2, 3);

int d = 0;
for (d = 0; d < SIZE; d++){
    printf("%d\n", sample2[d]);
}

I am assuming SIZE is the size of the array.

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