Given A Matrix Of Integers, Return The Sum Of The Elements Along The Main Diagonal (Top Left Bottom Right) Signature:  #include extern int diagonal(int*" v:shapes="Picture_x0020_5">

1-1. Given a matrix of integers, return the sum of the elements along the main diagonal (top left bottom right) Signature: int diagonal (int array[4][4]) (Note. This function should be placed in function-1-1.cpp and the matching main function in main-1-1.cpp)