add solution

Python/flatten-2d-vector.py

@@ -0,0 +1,36 @@
+# Time:  O(1)
+# Space: O(1)
+
+class Vector2D:
+    x, x_len = 0, 0
+    y, y_len = 0, 0
+    vec = None
+
+    # Initialize your data structure here.
+    # @param {integer[][]} vec2d
+    def __init__(self, vec2d):
+        self.vec = vec2d
+        self.x = 0
+        self.x_len = len(self.vec)
+        if self.x != self.x_len:
+            self.y = 0
+            self.y_len = len(self.vec[self.x])
+            self.adjustNextIter()
+
+    # @return {integer}
+    def next(self):
+        ret = self.vec[self.x][self.y]
+        self.y += 1
+        self.adjustNextIter()
+        return ret
+
+    # @return {boolean}
+    def hasNext(self):
+        return self.x != self.x_len and self.y != self.y_len
+
+    def adjustNextIter(self):
+        while self.x != self.x_len and self.y == self.y_len: 
+            self.x += 1
+            if self.x != self.x_len:
+                self.y = 0
+                self.y_len = len(self.vec[self.x])