I have two NSMutableArray filled with data object. how do I compare both array and merge if any change found.

ex:
`Array1= index(0) userName = {'a',1,'address'}`
`index(1) userName = {'b',2,'address'}`

`Array2= index(0) userName = {'c',3,'address'}`
`index (1) userName = {'b',2,'address'}`

Result is: 
`Array= index(0) userName = {'a',1,'address'}`
`index (1) userName = {'b',2,'address'}`
`index(2) userName = {'c',3,'address'}`

Please help