205. Isomorphic Strings

Author: remy727

README.md

@@ -41,6 +41,7 @@
 | 121 | Best Time to Buy and Sell Stock | [Ruby](./algorithms/ruby/0121-best-time-to-buy-and-sell-stock.rb) | Easy |
 | 129 | Sum Root to Leaf Numbers | [Ruby](./algorithms/ruby/0129-sum-root-to-leaf-numbers.rb) | Medium |
 | 142 | Linked List Cycle II | [Ruby](./algorithms/ruby/0142-linked-list-cycle-ii.rb) | Medium |
+| 205 | Isomorphic Strings | [Ruby](./algorithms/ruby/0205-isomorphic-strings.rb) | Easy |
 | 208 | Implement Trie (Prefix Tree) | [Ruby](./algorithms/ruby/0208-implement-trie-prefix-tree.rb) | Medium |
 | 211 | Design Add and Search Words Data Structure | [Ruby](./algorithms/ruby/0211-design-add-and-search-words-data-structure.rb) | Medium |
 | 226 | Invert Binary Tree | [Ruby](./algorithms/ruby/0226-invert-binary-tree.rb) | Easy |

algorithms/ruby/0205-isomorphic-strings.rb

@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+# 205. Isomorphic Strings
+# https://leetcode.com/problems/isomorphic-strings
+
+=begin
+
+Given two strings s and t, determine if they are isomorphic.
+
+Two strings s and t are isomorphic if the characters in s can be replaced to get t.
+
+All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.
+
+### Example 1:
+
+Input: s = "egg", t = "add"
+Output: true
+
+### Example 2:
+
+Input: s = "foo", t = "bar"
+Output: false
+
+### Example 3:
+
+Input: s = "paper", t = "title"
+Output: true
+
+### Constraints:
+
+* 1 <= s.length <= 5 * 104
+* t.length == s.length
+* s and t consist of any valid ascii character.
+
+=end
+
+# Runtime 258 ms
+# Memory 211.3 MB
+# @param {String} s
+# @param {String} t
+# @return {Boolean}
+def is_isomorphic(s, t)
+  ms = {}
+  mt = {}
+  n = s.length
+  i = 0
+
+  while i < n && ms[s[i]] == mt[t[i]]
+    ms[s[i]] = mt[t[i]] = i + 1
+    i += 1
+  end
+
+  i == n
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_is_isomorphic < Test::Unit::TestCase
+  def test_
+    assert_equal true, is_isomorphic("egg", "add")
+    assert_equal false, is_isomorphic("foo", "bar")
+    assert_equal true, is_isomorphic("paper", "title")
+  end
+end