Returns index of extra element in arr1 [ ] . n is size of arr2 [ ] . Size of arr1 [ ] is n - 1.
< ? php function findExtra ( $ arr1 , $ arr2 , $ n ) { for ( $ i = 0 ; $ i < $ n ; $ i ++ ) if ( $ arr1 [ $ i ] != $ arr2 [ $ i ] ) return $ i ; return $ n ; }