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: Actually, you don't, though it can certainly be done that way. — Scott Hunter
– Scott Hunter, Commented Dec 9, 2014 at 1:02

iameven · Accepted Answer · 2014-12-09 02:07:50Z

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;
}

answered Dec 9, 2014 at 2:07

iameven

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Comments

Scott Hunter · Accepted Answer · 2014-12-09 01:26:06Z

0

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).

answered Dec 9, 2014 at 1:26

Scott Hunter

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1 Comment

byerlyfactor Over a year ago

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.

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