Array - 19: Find the first repeating value in array

Code: thecodingsimplified.com/find-...
Solution:
- We'll take a Set & a variable firstRepeat
- We'll iterate from last element & if value doesn't present in Set, put this value in Set.
- If element already present in Set, update this value with firstRepeat.
- The last updated value in firstRepeat will contain the repeated value, as we'll movinf from back.
- Time Complexity: O(n) for iterating the complete array
- Space Complexity: O(n) for Set
Please check video for more info:
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[@anjalisingh-sx5ct]

int min= -1;
//If element already in hash set
if (myset.find(arr[i]) != myset.end())
min = i;
else // Else add element to hash set
myset.insert(arr[i]);
This is c++ code i didn't get third line what myset.end( ) points to end of set...then how will it find the repeated number...pls help

[@YashRaithatha1989]

Good work. Keep it up !

[@CodingSimplified]

Thanks

[@nethravathim8422]

If the array has 2,4,4,5,5,7,7 in this case first occurance is 4 but set will return 7. But the answer has to be 4 because this is the first reperating occurance in the array. Explain me this if i am wrong

[@rajasakthikumarrajendran5806]

can we do it with linked hashmap

[@sourav5562]

I do not understand what will happen if we begin from starting. and if we take Tree set? explain plz

[@CodingSimplified]

If you do from start, you can't be sure about first repeated value. Just take the example mentioned in video & try from starting.
- Treeset won't help here. We use TreeSet for sorting & here we don't require sorting. Thanks

[@pranitapasalkar5533]

How to solve this using brute force

[@anjalisingh-sx5ct]

Other than brute , hashing .....
Any approach????

[@piyushmathpal4244]

yes
if(s.indexOf(i)!=s.lastIndexOf(i))
return a.charAt(i);

[@codeforthrone9569]

any way to do this with 2 pointers method???

[@anjalisingh-sx5ct]

It won't work

[@032_ritiksati7]

@@anjalisingh-sx5ct why?? Can u plz explain