refuctor ex9_31_32_34.cpp and added 9.33

1. 9.31 have an other case: forward_list
2. 9.32 it's not always illegal.
3. 9.34 infinite loop added fixed solution.

ch09/README.md

@@ -208,3 +208,8 @@ that takes a single argument place on the element type?
 
 If the container holds elements of a class type and resize adds elements
 we **must supply an initializer** or the element type must have a **default constructor**.
+
+## Exercise 9.31 [use list](ex9_31_1.cpp) | [use forward_list](ex9_31_2.cpp)
+## [Exercise 9.32](ex9_32.cpp)
+## [Exercise 9.33](ex9_33.cpp)
+## [Exercise 9.34](ex9_34.cpp)

ch09/ex9_31_1.cpp

@@ -0,0 +1,37 @@
+//
+//  ex9_31.cpp
+//  Exercise 9.31 
+//
+//  Created by pezy on 12/3/14.
+//  Copyright (c) 2014 pezy. All rights reserved.
+//
+//  @Brief  The program on page 354 to remove even-valued elements and 
+//          duplicate odd ones will not work on a list or forward_list. Why? 
+//          Revise the program so that it works on these types as well. 
+//  @list   iter += 2; -> advance(iter, 2);
+//
+
+#include <iostream>
+#include <list>
+
+using std::list; using std::cout; using std::endl; using std::advance;
+
+int main()
+{
+    list<int> vi = {0,1,2,3,4,5,6,7,8,9}; 
+    auto iter = vi.begin(); 
+    while (iter != vi.end()) {    
+        if (*iter % 2) {        
+            iter = vi.insert(iter, *iter);  
+            advance(iter, 2); 
+        } else        
+            iter = vi.erase(iter); 
+    }
+
+    for (auto i : vi)
+        cout << i << " ";
+
+    return 0;
+}
+
+

ch09/ex9_31_2.cpp

@@ -0,0 +1,40 @@
+//
+//  ex9_31.cpp
+//  Exercise 9.31 
+//
+//  Created by pezy on 12/3/14.
+//  Copyright (c) 2014 pezy. All rights reserved.
+//
+//  @Brief  The program on page 354 to remove even-valued elements and 
+//          duplicate odd ones will not work on a list or forward_list. Why? 
+//          Revise the program so that it works on these types as well. 
+//  @forward_list   1. vi.insert -> vi.insert_after
+//                  2. iter += 2; -> advance(iter, 2);
+//                  3. vi.erase -> vi.erase_after
+//                  4. added iterator prev, and edit some detail
+
+#include <iostream>
+#include <forward_list>
+
+using std::forward_list; using std::cout; using std::endl; using std::advance;
+
+int main()
+{
+    forward_list<int> vi = {0,1,2,3,4,5,6,7,8,9}; 
+    auto iter = vi.begin(), prev = vi.before_begin();
+    while (iter != vi.end()) {    
+        if (*iter % 2) {        
+            iter = vi.insert_after(prev, *iter);   
+            advance(iter, 2);
+            advance(prev, 2);
+        } else        
+            iter = vi.erase_after(prev);
+    }
+
+    for (auto i : vi)
+        cout << i << " ";
+
+    return 0;
+}
+
+

ch09/ex9_32.cpp

@@ -0,0 +1,38 @@
+//
+//  ex9_32.cpp
+//  Exercise 9.32 
+//
+//  Created by pezy on 12/3/14.
+//  Copyright (c) 2014 pezy. All rights reserved.
+//
+//  @Brief  In the program onpage 354 would it be legal to write the call to insert as follows? 
+//          If not, why not?
+//          iter = vi.insert(iter, *iter++); 
+//  @Answer - If only changed this, it's illegal obviously. like @Mooophy said:
+//          "*iter++  can result in deferencing an item out of range causing a runtime error."
+//          - If change "iter += 2;" to "++iter;" after the call. It is legal.(follow codes)
+
+#include <iostream>
+#include <vector>
+
+using std::vector; using std::cout; using std::endl;
+
+int main()
+{
+    vector<int> vi = {0,1,2,3,4,5,6,7,8,9}; 
+    auto iter = vi.begin(); 
+    while (iter != vi.end()) {    
+        if (*iter % 2) {        
+            iter = vi.insert(iter, *iter++);  
+            ++iter;
+        } else        
+            iter = vi.erase(iter); 
+    }
+
+    for (auto i : vi)
+        cout << i << " ";
+
+    return 0;
+}
+
+

ch09/ex9_33.cpp

@@ -0,0 +1,34 @@
+//
+//  ex9_33.cpp
+//  Exercise 9.33 
+//
+//  Created by pezy on 12/3/14.
+//  Copyright (c) 2014 pezy. All rights reserved.
+//
+//  @Brief  In the final example in this section what would happen 
+//          if we did not assign the result of insert to begin? 
+//          Write a program that omits this assignment to see if your expectation was correct.  
+//  @Answer crash, cause the iterator is invalid after insert.
+
+#include <iostream>
+#include <vector>
+
+using std::vector; using std::cout; using std::endl;
+
+int main()
+{
+    vector<int> v{1,2,3,4,5,6,7,8,9}; 
+    auto begin = v.begin();
+    while (begin != v.end()) {
+        ++begin;
+        /*begin = */v.insert(begin, 42);
+        ++begin;
+    } 
+
+    for (auto i : v)
+        cout << i << " ";
+
+    return 0;
+}
+
+

ch09/ex9_34.cpp

@@ -0,0 +1,36 @@
+//
+//  ex9_32.cpp
+//  Exercise 9.32 
+//
+//  Created by pezy on 12/3/14.
+//  Copyright (c) 2014 pezy. All rights reserved.
+//
+//  @Brief  Assuming vi is a container of ints that includes even and odd values, 
+//          predict the behavior of the following loop. 
+//          After you've analyzed this loop, write a program to test whether your expectations were correct.
+//  @Answer "infinite loop". Casue the `++iter` out of the `while` loop. But even through add brackets it is still infinite loop.
+//          Fixed following.
+
+#include <iostream>
+#include <vector>
+
+using std::vector; using std::cout; using std::endl;
+
+int main()
+{
+    vector<int> vi = {0,1,2,3,4,5,6,7,8,9}; 
+    auto iter = vi.begin(); 
+    while (iter != vi.end())
+    {    
+        if (*iter % 2)        
+            iter = vi.insert(iter, *iter++);    
+        ++iter;
+    }
+
+    for (auto i : vi)
+        cout << i << " ";
+
+    return 0;
+}
+
+