add unix path and target sum

Author: sagivo

README.md

@@ -17,6 +17,7 @@ This is my way of saying - change your interview style. There are lots of smart
 | [House Robber](https://leetcode.com/problems/house-robber/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/house-robber.rb) |
 | [Coin change](https://leetcode.com/problems/coin-change/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/coin-change.rb) |
 | [Decode Strings](https://leetcode.com/problems/decode-string/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/decode_string.rb) |
+| [Unix path](https://leetcode.com/problems/simplify-path/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/simplify_path.rb) |
 | [Array Product](https://leetcode.com/problems/product-of-array-except-self/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/product-of-array.rb) |
 | [Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/top-k-elements.rb) |
 | [Sum 4 arrays](https://leetcode.com/problems/4sum-ii/description/) | [click](https://github.com/sagivo/algorithms/blob/master/src/4-sum.rb) |

src/simlify_path.rb

@@ -0,0 +1,19 @@
+# @param {String} path
+# @return {String}
+def simplify_path(path)
+ dirs = path.split("/")
+ stack = []
+
+ dirs.each do |dir|
+ next if dir.empty? || dir == "."
+ if dir == ".."
+ stack.pop unless stack.empty?
+ else
+ stack.push(dir)
+ end
+ end
+
+ "/" + stack.join("/")
+end
+
+p simplify_path("/a/./b/../../c/") # => "/c"

src/target_sum.rb

@@ -0,0 +1,15 @@
+# @param {Integer[]} nums
+# @param {Integer} s
+# @return {Integer}
+def find_target_sum_ways(nums, s, i = 0, dp = {})
+ return dp["#{s}-#{i}"] if dp["#{s}-#{i}"]
+ if i == nums.size
+ return dp["#{s}-#{i}"] = s == 0 ? 1 : 0
+ end
+
+ return dp["#{s}-#{i}"] ||=
+ find_target_sum_ways(nums, s + nums[i], i+1, dp) +
+ find_target_sum_ways(nums, s - nums[i], i+1, dp)
+end
+
+p find_target_sum_ways([1, 1, 1, 1, 1], 3) # => 5