I want to know what is wrong with my logic when my output is supposed to be as follows:
There are two arrays of integers and that prints the index of the first occurrence of the first list in the second list.For example, suppose that you have these arrays:
int[] list1 = {1, 3, 6};
int[] list2 = {1, 3, 5, 8, 12, 1, 3, 17, 1, 3, 6, 9, 1, 3, 6};
Then the call indexOf(list1, list2) should return 8 because the sequence of values stored in list1 appears in list2 starting at index 8. The list1 appears twice in list2, starting at position 8 and starting at position 12. The method should return the first such position.
Currently, my code does not print anything...
public static void indexOf(int[] arr1, int[] arr2){
for(int i = 0; i < arr2.length; i++){
for(int j = 0; j < arr1.length; j++){
if(arr1[j] != arr2[i]){
break;
}
if(j == arr1.length -1){
System.out.println(i);
break;
}
}
}
}
arr1[j] != arr2[i] should be arr1[j] != arr2[i + j]
Why
In each iteration of the inner loop you should be comparing each element of the original subsequence (arr1[j]) with the corresponding element in the current subsequence you have sliced from arr2 (arr2[i + j]). You were comparing to just the first element in the current slice.
Moreover
Your loop termination condition should be i + (arr1.length - 1) < arr2.length to avoid accessing out of bound index if the last element in arr2 was 1 (or in general equal to the first element in arr1).
...also
The second break should be return to print the first occurrence as you stated.
Full Code
public static void indexOf(int[] arr1, int[] arr2) {
for(int i = 0; i + (arr1.length - 1) < arr2.length; i++) {
for(int j = 0; j < arr1.length; j++) {
if(arr1[j] != arr2[i + j]) {
break;
}
if(j == (arr1.length - 1)){
System.out.println(i);
break; // break to print all the occurrences. return to print only the first.
}
}
}