fix: forgot commit the "Find the Difference"

Author: haoel

algorithms/cpp/findTheDifference/FindTheDifference.cpp

@@ -0,0 +1,38 @@
+// Source : https://leetcode.com/problems/find-the-difference/
+// Author : Hao Chen
+// Date   : 2016-09-08
+
+/*************************************************************************************** 
+ *
+ * Given two strings s and t which consist of only lowercase letters.
+ * 
+ * String t is generated by random shuffling string s and then add one more letter at a 
+ * random position.
+ * 
+ * Find the letter that was added in t.
+ * 
+ * Example:
+ * 
+ * Input:
+ * s = "abcd"
+ * t = "abcde"
+ * 
+ * Output:
+ * e
+ * 
+ * Explanation:
+ * 'e' is the letter that was added.
+ ***************************************************************************************/
+
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        unordered_map<char, int> m;
+        for(auto c : s) m[c]++;
+        for(auto c : t) {
+            m[c]--;
+            if (m[c] < 0) return c;
+        }
+        return '\0';
+    }
+};