add flatten.cpp

Author: kamyu104

C++/coundAndSay.cpp

@@ -0,0 +1,24 @@
+// Time Complexity: O(n^2)
+// Space Complexity: O(n)
+
+class Solution {
+    public:
+        string countAndSay(int n) {
+            string s{"1"};
+            while(--n) {
+                s = getNext(s);
+            }
+            return s;
+        }
+
+    private:
+        string getNext(const string &s) {
+            stringstream ss;
+            for(auto i = s.begin(); i != s.end();) {
+                auto j = find_if(i, s.end(), bind1st(not_equal_to<char>(), *i));
+                ss << distance(i, j) << *i;
+                i = j;
+            }
+            return ss.str();
+        }
+};