flatten 2d vector

Author: fishercoder1534

MEDIUM/src/medium/Flatten2DVector.java

@@ -0,0 +1,38 @@
+package medium;
+
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+public class Flatten2DVector {
+
+}
+
+class Vector2D implements Iterator<Integer> {
+    private Queue<Integer> cache;
+    private List<List<Integer>> vec2d;
+    
+    public Vector2D(List<List<Integer>> vec2d) {
+        this.vec2d = vec2d;
+        this.cache = new LinkedList<Integer>();
+        if(vec2d != null && vec2d.size() > 0){
+            for(List<Integer> list : vec2d){
+                for(int i : list){
+                    cache.offer(i);
+                }
+            }
+        }
+    }
+    
+    @Override
+    public Integer next() {
+        return cache.poll();
+    }
+
+    @Override
+    public boolean hasNext() {
+        return !cache.isEmpty();
+    }
+}
+

README.md

@@ -63,6 +63,7 @@
 |259|[3Sum Smaller](https://leetcode.com/problems/3sum-smaller/)|[Solution](../../blob/master/MEDIUM/src/medium/_3Sum_Smaller.java)| O(n^2)|O(1) | Medium|
 |257|[Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths/)|[Solution](../../blob/master/EASY/src/easy/BinaryTreePaths.java) | O(n*h) | O(h) | DFS/Recursion
 |252|[Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)|[Solution](../../blob/master/EASY/src/easy/MeetingRooms.java) | O(nlogn) | O(1) | 
+|251|[Flatten 2D Vector](https://leetcode.com/problems/flatten-2d-vector/)|[Solution](../../blob/master/MEDIUM/src/medium/Flatten2DVector.java)| O(1)|O(m*n) | Medium| 
 |250|[Count Univalue Subtrees](https://leetcode.com/problems/count-univalue-subtrees/)|[Solution](../../blob/master/MEDIUM/src/medium/CountUnivalueSubtrees.java)| O(n)|O(h) | Medium| DFS
 |249|[Group Shifted Strings](https://leetcode.com/problems/group-shifted-strings/)|[Solution](../../blob/master/EASY/src/easy/GroupShiftedStrings.java) | O(nlogn) | O(n) | 
 |246|[Strobogrammatic Number](https://leetcode.com/problems/strobogrammatic-number/)|[Solution](../../blob/master/EASY/src/easy/StrobogrammaticNumber.java) | O(n) | O(1) |