collection = [ [1, 'one'], [2, 'two'], [3, 'three'],
[4, 'four'], [5, 'five']
]
collection.inject({}) do |hash, value|
hash[value.first] = value.last
hash
end
p collection
# => {5=>"five", 1=>"one", 2=>"two", 3=>"three", 4=>"four"}