Added 049_Group_Anagrams.java, 129_Contains_Duplicate_II.java (qiyuangong#72)

* Added java solution for 049_Group_Anagrams.java
* Added java solution for 129_Contains_Duplicate_II.java

Contributed by @BHwi

Author: BHwi

java/049_Group_Anagrams.java

@@ -0,0 +1,42 @@
+class Solution {
+    public List<List<String>> groupAnagrams(String[] strs) {
+        int[][] alphabets = new int[strs.length]['z' - 'a' + 1];
+        
+        for(int i = 0; i < strs.length; i++) {
+            String str = strs[i];
+            
+            for(int j = 0; j < str.length(); j++) 
+                alphabets[i][str.charAt(j) - 'a']++;
+        }
+        
+        boolean[] visited = new boolean[strs.length];
+        
+        List<List<String>> answer = new ArrayList<>();
+        
+        for(int i = 0; i < strs.length; i++) {
+            if(visited[i]) continue;
+            
+            List<String> list = new ArrayList<>();
+            
+            for(int j = i; j < strs.length; j++) {
+                if(visited[j]) continue;
+                if(isAnagram(alphabets[i], alphabets[j])) {
+                    list.add(strs[j]);
+                    visited[j] = true;
+                }
+            }
+            
+            answer.add(list);
+        }
+        
+        return answer;
+    }
+    
+    public boolean isAnagram(int[] arr1, int[] arr2) {
+        for(int i = 0; i < arr1.length; i++) {
+            if(arr1[i] != arr2[i])
+                return false;
+        }
+        return true;
+    }
+}

java/219_Contains_Duplicate_II.java

@@ -0,0 +1,44 @@
+import java.util.*;
+
+class Solution {
+  /*
+   * I have to save indice for each index.
+   * So I use the HashMap<Integer, List<Integer>>
+   */
+
+    public boolean containsNearbyDuplicate(int[] nums, int k) {
+        HashMap<Integer, List<Integer>> map = new HashMap<>();
+        
+        for(int i = 0; i < nums.length; i++) {
+            if(!map.containsKey(nums[i])) {
+                map.put(nums[i], new ArrayList<>());
+            }
+            map.get(nums[i]).add(i);
+        }
+        
+		// use Iterator to find appropriate two indice.
+		// Each list guarantee ascending.
+		// So list.get(i) and list.get(i + 1) is minimum.
+        Iterator<Integer> keys = map.keySet().iterator();
+        boolean answer = false;
+        
+        while(keys.hasNext()) {
+            int key = keys.next();
+            List<Integer> list = map.get(key);
+            
+            if(list.size() < 2) continue;
+            
+            for(int i = 1; i < list.size(); i++) {
+                int a = list.get(i - 1);
+                int b = list.get(i);
+                
+                if(b - a <= k) {
+                    answer = true;
+                    break;
+                }
+            }
+            if(answer) break;
+        }
+        return answer;
+    }
+}