fixed bug pass 11.36's requesting

ch11/README.md

@@ -100,3 +100,22 @@ std::pair<std::map<std::string, std::vector<int>>::iterator, bool> // return
 ## [Exercise 11.31](ex11_31.cpp)
 ## [Exercise 11.32](ex11_32.cpp)
 ## [Exercise 11.33](ex11_33.cpp)
+
+## Exercise 11.34:
+>What would happen if we used the subscript operator instead of find in the transform function?
+
+If the subscript operator was used instead, it would add the given key into the map when no element with matching key was found.
+
+## Exercise 11.35:
+>In buildMap, what effect, if any, would there be from rewriting `trans_map[key] = value.substr(1);` as `trans_map.insert({key, value.substr(1)})`?
+
+- use subscript operator: if a word does appear multiple times, our loops will put the **last** corresponding phrase into trans_map
+- use `insert`: if a word does appear multiple times, our loops will put the **first** corresponding phrase into trans_map
+
+## Exercise 11.36:
+>Our program does no checking on the validity of either input file. In particular, it assumes that the rules in the transformation file are all sensible.
+What would happen if a line in that file has a key, one space, and then the end of the line? Predict the behavior and then check it against your version of the program.
+
+we added a file that name "word_transformation_bad.txt" to folder `data`. the file only has a key, one space.
+
+the program of 11.33 don't influenced by that.

ch11/ex11_33.cpp

@@ -42,7 +42,7 @@ void word_transform(ifstream &map, ifstream &input)
 
 int main()
 {
-    ifstream ifs_map("../data/word_transformation.txt"), ifs_content("../data/given_to_transform.txt");
+    ifstream ifs_map("../data/word_transformation_bad.txt"), ifs_content("../data/given_to_transform.txt");
     if (ifs_map && ifs_content) word_transform(ifs_map, ifs_content);
     else std::cerr << "can't find the documents." << std::endl;
 }

data/word_transformation_bad.txt

@@ -0,0 +1 @@
+l8r