M[189][168] Random char elements (x,y,z,w,r)

How can i make a C++ code for matrix char M[189][168], which consists of elements ('x','y','z','w','r'), as well

x as an element should be repeated 50 times

y as an element should be repeated 50 times

z as an element should be repeated 86 times

w as an element should be repeated 86 times

r as an element should be repeated 85 times

the matrix's elements should be randomly recognized (no two similar elements at the same diagonal)