Check to see if an array is contained within another array

Question

The problem is: Check to see if the array arr2 is contained within the arr1 in the same order. The arr2 could be contained anywhere with in arr1.

public boolean contains(String[] arr1, String[] arr2)
{
 int length = 0;
 if(arr2.length > arr1.length)
 return false;
 for(int i = 0; i < arr2.length; i++)
 {
 if(arr2[i] == arr1[i])
 length++;
 }
 if(length == arr2.length)
 return true;
 else
 return false;
}

TESTER: contains({"1", "2", "3"}, {"1", "2"}) → true

RUN: TRUE

TESTER: contains({"1", "2", "3"}, {"2", "3"}) → true

RUN: FALSE

TESTER: contains({"1", "2", "3"}, {"2", "1"}) → false

RUN: TRUE

TESTER: contains({"MARY", "A", "LITTLE", "LAMB"}, {"A", "LITTLE", "LAMB"}) → true

RUN: FALSE

TESTER: contains({"MARY", "A", "LITTLE", "LAMB"}, {"MARY", "A", "LITTLE", "LAMB"}) → true

RUN: TRUE

.

I don't know where I'm going wrong. Thanks for help.

• mdnghtblue: Hint: you need a nested for loop.
• Scott Hunter: @mdnghtblue: Actually, you don't, though it can certainly be done that way.

Answer 1

• use arr[1].equals(arr[2]) instead arr[1] == arr[2]
• should judge in the loop not before loop

I modify the code like it:

public static boolean contains(String[] arr1, String[] arr2) {
 int length = 0;
 for (int i = 0; i < arr1.length; i++) {
 if (arr2[length].equals(arr1[i])) {
 length++;
 } else {
 length = 0;
 }
 if (length == arr2.length)
 return true;
 }
 return false;
}

Answer 2

You are only comparing both arrays from the beginning; you need to also consider the cases when you start comparing at a different location in arr1. For example, you would get TRUE in the second example if you started comparing at the second element of arr1 (same for the fourth example).

• byerlyfactor: So how do I start comparing at the second element of arr1? I tried at the if statement to do if(arr2[i] == arr1[i] || arr2[i] == arr1[i+1]) but it doens't work.