adding lecture 16

leetcode/p49_group_anagrams.cpp

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    vector<vector<string>> groupAnagrams(vector<string>& strs) {
+        std::vector<std::vector<std::string> > result;
+        int size = strs.size();
+        // create a map, key is the word, value is the anagram group.
+        std::map<std::string, std::vector<std::string> > map1;
+        for(int i=0; i<size; i++){
+            std::string s = strs[i];
+            // ate, eat, tea will be the same word after sorting.
+            sort(s.begin(), s.end());
+            // the most tricky line, this is the magic of [] in map.
+            map1[s].push_back(strs[i]);
+        }
+        // use the map
+        std::map<std::string, std::vector<std::string> >::iterator itr;
+        itr = map1.begin();
+        while(itr != map1.end()){
+            // question: do you understand why we do this push_back?
+            result.push_back(itr->second);
+            itr++;
+        }
+        return result;
+    }
+};