Using $C++,$ define an integer array $($e$.$g$.,$ size is $20)$ and a target number $($e$.$g$.50),$

assign the array with random numbers in $(0,20),$ then define a function to find all

unique number pairs of the array such that each pair of the numbers adds up to the

target number. Print the number pairs and their original indices in the array. For

example, given array $A=\{5,3,4,2,6,7\},$ target $=9,$ the number pairs are $(5,4),(3,6),$

and $(2,7).$ Their index info is $(0,2),(1,4),$ and $(3,5).$