ruby - Changing an array -

i created array way:

 arr = array.new(4, array.new(4, '*')) 

when try change 1 element, example first element of first array:

 arr[0][0] = 3 

then every first element changed.

 print arr  [[3, "*", "*", "*"], [3, "*", "*", "*"], [3, "*", "*", "*"], [3, "*", "*", "*"]] 

can explain why happening?

do:

arr = array.new(4) { array.new(4, '*') } 

ruby array in fact set of pointers, points onto other objects n memory. in code pointers point same object created array.new(4, '*'). if, instead of value, pass block, block executed every element of array, each pointer point new object in memory.

in fact, code above still have similar issue string '*'. should use same method fix it:

arr = array.new(4) { array.new(4) { '*' } }