Merge pull request #207 from theforestvn88/jan

2375

Author: theforestvn88

2301-2400/2375_construct_smallest_number_from_di_string.rb

@@ -0,0 +1,20 @@
+# @param {String} pattern
+# @return {String}
+def smallest_number(pattern, result = [], i = -1, prev_num = 0, prev_pat = "I", used = Array.new(10, false))
+    return result.join if i == pattern.size
+
+    (1..9).each { |j|
+        if !used[j] && (prev_pat == "D" ? (j < prev_num) : (j > prev_num))
+            result << j
+            used[j] = true
+            
+            found = smallest_number(pattern, result, i + 1, j, pattern[i + 1], used)
+            return found unless found.nil?
+
+            result.pop
+            used[j] = false
+        end
+    }
+    
+    nil
+end