add binary numbers

Author: sagivo

README.md

@@ -29,6 +29,7 @@ This is my way of saying - change your interview style. There are lots of smart
 | [Dijkstra's shortest path between two nodes](https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm) | [click](https://github.com/sagivo/algorithms/blob/master/src/dijkstra.rb) |
 | [Kruskal's minimum spanning tree algorithm](http://en.wikipedia.org/wiki/Kruskal%27s_algorithm) | [click](https://github.com/sagivo/algorithms/blob/master/src/kruskal.rb) |
 | [Find the square root of a number](https://en.wikipedia.org/wiki/Newton%27s_method) | [click](https://github.com/sagivo/algorithms/blob/master/src/sq_root.rb) |
+| [Add two binary numbers](https://leetcode.com/problems/add-binary/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/add_binary.rb) |
 | [Binary search](https://en.wikipedia.org/wiki/Binary_search_algorithm) | [click](https://github.com/sagivo/algorithms/blob/master/src/binary_search.rb) |
 | [Longest increasing subsequence](http://en.wikipedia.org/wiki/Longest_increasing_subsequence) | [click](https://github.com/sagivo/algorithms/blob/master/src/longest_increasing_subsequence.rb) |
 | [Find all permutations of array](https://en.wikipedia.org/wiki/Permutation) | [click](https://github.com/sagivo/algorithms/blob/master/src/permutations.rb) |

src/add_binary.rb

@@ -0,0 +1,23 @@
+# problem: https://leetcode.com/problems/add-binary
+# @param {String} a
+# @param {String} b
+# @return {String}
+def add_binary(a, b)
+ i = 0
+ cerry = 0
+ res = ''
+
+ while (i < a.size) || (i < b.size) do
+ a1 = i<a.size ? a[a.size-1 - i].to_i : 0
+ b1 = i<b.size ? b[b.size-1 - i].to_i : 0
+ num = a1 ^ b1 ^ cerry
+ res += num.to_s
+ cerry = (a1 + b1 + cerry) >= 2 ? 1 : 0
+ i+=1
+ end
+ res += '1' if cerry == 1
+
+ return res.reverse
+end
+
+p add_binary('1010','1011') #=> '10101'

src/phone.rb

@@ -1,31 +1,31 @@
-def letters_for_number num 
+def letters_for_number num
  case num
  when 0, 1
  [num]
- when 2 
- ['A', 'B', 'C'] 
- when 3 
+ when 2
+ ['A', 'B', 'C']
+ when 3
  ['D', 'E', 'F']
- when 4 
+ when 4
  ['G', 'H', 'I']
- when 5 
+ when 5
  ['J', 'K', 'L']
- when 6 
+ when 6
  ['M', 'N', 'O']
- when 7 
+ when 7
  ['P', 'Q', 'R', 'S']
- when 8 
+ when 8
  ['T', 'U', 'V']
- when 9 
+ when 9
  ['W' ,'X', 'Y', 'Z']
  else
  []
- end 
+ end
 end
 
 def join_sets set, i = 0, str = '', result = []
  return result << str if str.size == set.size
- for item in set[i] 
+ for item in set[i]
  join_sets set, i.succ, str + item.to_s, result
  end
  result