Searching for matching elements between 2 arrays in C - arrays

Question

Question
There are two arrays, one contains a large number of numbers (arr1) that may have a few repeating sequences for example 1,2,4 might repeat multiple times in this array. There is another array (arr2) that will be assigned by the user.
I need a way to search arr1 for the exact input the user gave for arr2. For a match to be valid, all the elements have to be in the exact same order as entered by the user.
For example, if the user enters 1,2,4,3 the program has to find 1,2,4,3 in that exact order in arr1, this means that 1,2,3,4 in arr1 should not be counted as a match. Below is what I have been able to come up with so far, but this returns true even if just the first element of the 2 arrays matches.
for (int i=0; i<size1; i++)
{
for (int j = 0; j<size2; j++)
{
if(arr1[i] == arr2[j])
{
printf("found a match %d", j);
break;
}
else if (arr1[i] != arr2[j])
{
printf("not match");
break;
}
Below is the complete code :-
#include <stdio.h>
#include <string.h>
int main()
{
int arr1[] = {1, 2, 4, 2, 2, 2, 1, 1, 2, 4, 3, 4, 4, 1, 2, 4, 4, 1, 3, 3};
int size1 = (int) (sizeof(arr1)/sizeof(arr1));
int arr2[] = {1, 2, 4};
int size2 = (int) (sizeof(arr2)/sizeof(arr2[0]));
int match = 0;
for (int i=0; i<size1; i++)
{
for (int j = 0; j < size2; j++) {
if (arr1[i] != arr2[j]) {
match = 1;
break;
}
}
}
if(match == 1){
printf("Not a match");
}else if(match == 0){
printf("The lists match");
}
return 0;
}
if you look at the arr1 and arr2, I need a way to return the index 0,7,13 and also this is still rough since arr2 is technically dynamic since it is assigned by the user and has no fixed size, only arr1 will have a fixed size.

Answer 1

Your question is similar to finding substrings in a string. But characters are replaced with integers.
Here is a program that will find the matches. It has some debug print statements to show how it works.
#include <stdio.h>
int g_Arr2_Changed=0; //----Global boolean if arr2 changes.
int main(int argc, const char *argv[])
{ int arr1[] = {1, 2, 4, 2, 2, 2, 1, 1, 2, 4, 3, 4, 4, 1, 2, 4, 4, 1, 3, 3};
int size1 = (int) (sizeof(arr1)/sizeof(int));
int arr2[] = {1, 2, 4};
int size2 = (int) (sizeof(arr2)/sizeof(int));
int patternStart = -1; //----Start pattern in arr1.
int nPatternMatch = 0; //----Number of ints matched so far.
for (int i=0; i<size1; i++)
{ int checkInt = arr1[i];
//printf("[%i](%i)", i, checkInt);
if (nPatternMatch == 0) //----No integers are matched yet.
{ //printf("<None>");
//----Is checkInt the start of arr2?
if (arr2[nPatternMatch] == checkInt)
{ patternStart=i; nPatternMatch++; //printf("<start>");
}
}
else //----At least one integer has been matched already.
{ //printf("<Some>");
//----Is checkInt a continuation?
if (arr2[nPatternMatch] == checkInt)
{ nPatternMatch++; //----Matched another integer.
//printf("<matched>");
}
else
{ //printf("<NotMatched>");
i = patternStart; //---- for() will add one.
patternStart = - 1;
nPatternMatch = 0; //----Not match. Start at next int.
}
}
//----If match found print and reset for next.
if (nPatternMatch == size2)
{ printf("Pattern found at %i\n", patternStart);
i = patternStart + 1;
patternStart = -1; nPatternMatch = 0;
}
//----Just in case the global variable says arr2 changed.
if (g_Arr2_Changed != 0) //----Start over.
{ //printf("<arr2 changed.>");
i=0; patternStart = -1; nPatternMatch = 0;
size2 = (int) (sizeof(arr2)/sizeof(int));
}
//printf("\n");
}
return 0;
}

Answer 2

This code will return a match for every character that is found in the same position in both lists.
So if you you want to verify the whole list, you should set an int, to identify if there is even one character that doesn't match in both lists.
If you want to show the list that match, you just have to print the whole list inside the second if.
int match = 0;
for (int i=0; i<size1; i++)
{
for (int j = 0; j < size2; j++) {
if (arr1[i] != arr2[j]) {
match = 1;
break;
}
}
if(match == 1){
printf("Not a match");
}else if(match == 0){
printf("The lists match");
printf("First character: %c", arr2[0]);
}
match = 0;
}

Answer 3

Would you please try the following:
#include <stdio.h>
int main()
{
int arr1[] = {1, 2, 4, 2, 2, 2, 1, 1, 2, 4, 3, 4, 4, 1, 2, 4, 4, 1, 3, 3};
int size1 = sizeof arr1 / sizeof arr1[0];
int arr2[] = {1, 2, 4};
int size2 = sizeof arr2 / sizeof arr2[0];
int match;
int i, j;
for (i = 0; i < size1 - size2 + 1; i++) {
match = 0;
for (j = 0; j < size2; j++) {
if (arr1[i + j] != arr2[j]) {
match = 1;
break;
}
}
if (! match) {
printf("matched at %d\n", i);
}
}
return 0;
}
It will output:
matched at 0
matched at 7
matched at 13
If you want to assign an array to the list of the matched indices, it will be easy for you to modify the code.