refuctor ex9_41 and move ex9_42 to README

ch09/README.md

@@ -253,3 +253,10 @@ svec.resize(svec.size()+svec.size()/2); // sets capacity to at least 3/2's size.
 |512  |1024    |
 |1000 |1024    |
 |1048 |1572    |
+
+## [Exercise 9.41](ex9_41.cpp)
+
+## Exercise 9.42:
+>Given that you want to read a character at a time into a string, and you know that you need to read at least 100 characters, how might you improve the performance of your program?
+
+Use member `reserve(120)` to allocate enough space for this string. (@Mooophy)

ch09/ex9_41.cpp

@@ -0,0 +1,24 @@
+//
+//  ex9_41.cpp
+//  Exercise 9.41
+//
+//  Created by pezy on 12/4/14.
+//  Copyright (c) 2014 pezy. All rights reserved.
+//
+//  @Brief  Write a program that initializes a string from a vector<char>.
+
+#include <iostream>
+#include <vector>
+#include <string>
+
+using std::vector; using std::cout; using std::endl; using std::string;
+
+int main()
+{
+    vector<char> vec{'p', 'e', 'z', 'y'};
+    string str(vec.begin(), vec.end());
+
+    cout << str << endl;
+
+    return 0;
+}