feat: add cpp solution to lcof problem: No.50

Author: maolonglong

lcof/面试题50. 第一个只出现一次的字符/README.md

@@ -83,6 +83,26 @@ var firstUniqChar = function (s) {
 };
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    char firstUniqChar(string s) {
+        unordered_map<char, bool> um;
+        for (char c : s) {
+            um[c] = um.find(c) == um.end();
+        }
+        for (char c : s) {
+            if (um[c]) {
+                return c;
+            }
+        }
+        return ' ';
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题50. 第一个只出现一次的字符/Solution.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    char firstUniqChar(string s) {
+        unordered_map<char, bool> um;
+        for (char c : s) {
+            um[c] = um.find(c) == um.end();
+        }
+        for (char c : s) {
+            if (um[c]) {
+                return c;
+            }
+        }
+        return ' ';
+    }
+};