From 0fed05c895c2e02c63004d20dff4985d2e4424d9 Mon Sep 17 00:00:00 2001
From: Yi Gu <ro.deliberate@gmail.com>
Date: Wed, 24 Aug 2016 23:43:56 -0700
Subject: [PATCH] [String] Add Solution to Ransom Note

---
 String/RansomNote.swift | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 String/RansomNote.swift

diff --git a/String/RansomNote.swift b/String/RansomNote.swift
new file mode 100644
index 00000000..b79ca95e
--- /dev/null
+++ b/String/RansomNote.swift
@@ -0,0 +1,39 @@
+/**
+ * Question Link: https://leetcode.com/problems/ransom-note/
+ * Primary idea: Use a dictionary to calculate the existence of characters in magazine 
+ *               and check with the ransom Note
+ *
+ * Time Complexity: O(n), Space Complexity: O(n)
+ */
+
+class RansomNote {
+    func canConstruct(ransomNote: String, _ magazine: String) -> Bool {
+        var magazineMap = _strToMap(magazine)
+        
+        for char in ransomNote.characters {
+            if magazineMap[char] == nil {
+                return false
+            } else if magazineMap[char] == 0 {
+                return false
+            } else {
+                magazineMap[char]! -= 1 
+            }
+        }
+        
+        return true
+    }
+    
+    private func _strToMap(magazine: String) -> [Character: Int] {
+        var res = [Character: Int]()
+        
+        for char in magazine.characters {
+            if res[char] == nil {
+                res[char] = 1
+            } else {
+                res[char]! += 1
+            }
+        }
+        
+        return res
+    }
+}
\ No newline at end of file