How to compare two arrays in C programming language? - c

Question

I want to compare two different arrays which are both int. One array is static and contains numbers from 1 to 10 and second arrays asks user to enter ten different numbers and the program checks which elements from both arrays are equal.
#include <stdio.h>
int main(void) {
int array1[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int array2[10];
int i;
for (i = 0; i < 11; i++) {
printf("Enter numbers: ");
scanf("%d", &array2);
}
for (i = 0; i < 11; i++) {
if (array1[i] != array2[i]) {
printf("Not equal \n");
} else {
printf("They are equal. \n");
}
}
}
The program always say not equal even if I enter a number that is equal to a number stored in first array.

Answer 1

scanf("%d", &array2);
You are never updating the index of array2 when getting a value from input.
Try
scanf("%d", &array2[i]);
As for comparing, you can also use memcmp to compare memory:
memcmp(array1, array2, sizeof(array1));

Answer 2

Arrays use zero based indices for a start. You are incorrectly populating array2 so you probably want to change your first loop to the following
for (i=0;i<10;i++)
{
printf("Enter numbers: ");
scanf("%d", &array2[i]);
}
as your current code is simply passing the address of array2 as argument to scanf.
Then change the second loop conditional to
for (i=0;i<10;i++)
in your comparison loop so that you do not access items beyond your array boundaries.
Currently your second loop is accessing items at indices 0 to 10 - but there are only 10 items present in array1 so you have undefined behaviour with your current code.

Answer 3

#include <stdio.h>
int main(void) {
int array1[] = {1,2,3,4,5,6,7,8,9,10};
int array2[10];
int i;
for (i=0;i<10;i++) { //fixed the range here
printf("Enter numbers: ");
scanf("%d", &array2[i]); //fixed the indexing
}
for (i=0;i<10;i++) { //fixed the range here
if (array1[i] != array2[i]) {
printf("Not equal \n");
}
else {
printf("They are equal. \n");
}
}
}

Answer 4

I am a beginner and I have this idea about comparing two arrays. Hope It might help someone like me.
/***compare two array: all elements are same or not(if not sorted)***/
#include<stdio.h>
int main()
{
int n;
scanf("%d", &n);
int array1[n], array2[n];
int i, j;
for(i=0; i<n; i++)
{
scanf("%d", &array1[i]);
}
for(i=0; i<n; i++)
{
scanf("%d", &array2[i]);
}
int flg=0;
for(i = 0; i < n; i++)
{
for(j=0; j<n; j++)
{
if(array1[i] == array2[j])
{
flg += 1;
break;
}
}
}
if(flg == n)
{
printf("All The Elements of array1 is present in array2... :)");
}
else
{
printf("All THe Elements of array1 is not present in array2 :(");
}
return 0;
}

Answer 5

I am trying to respond to the answer, even though I am a beginner to C program.
According to your program written above, you are inputting and holding values to int array2[10] which has 11 elements.
Remember that the first element of this array is indexed by zero. Ex: array2[0], until it reaches the last element which is array2[10], you have counted 11.
Now array1 has the pre-defined values write which will be compared to your input values. Enter and store your values into array2[].
#include <stdio.h>
int main(void) {
int array1[] = {1,2,3,4,5,6,7,8,9,10};
int array2[10];
int i;
for (i=0;i<10;i++) { //fixed the range here
printf("Enter numbers: ");
scanf("%d", &array2[i]); //fixed the indexing
if (array1[i] != array2[i]) {
printf("Not equal \n");
}
else {
printf("They are equal. \n");
}
}
}