Merge pull request #2602 from markwang1992/110-isBalanced

110.平衡二叉树增加Go迭代法

Author: youngyangyang04

problems/0110.平衡二叉树.md

@@ -623,6 +623,8 @@ class Solution:
 ```
 ### Go:
 
+递归法
+
 ```Go
 func isBalanced(root *TreeNode) bool {
     h := getHeight(root)
@@ -653,6 +655,64 @@ func max(a, b int) int {
 }
 ```
 
+迭代法
+
+```Go
+func isBalanced(root *TreeNode) bool {
+    st := make([]*TreeNode, 0)
+    if root == nil {
+        return true
+    }
+    st = append(st, root)
+    for len(st) > 0 {
+        node := st[len(st)-1]
+        st = st[:len(st)-1]
+        if math.Abs(float64(getDepth(node.Left)) - float64(getDepth(node.Right))) > 1 {
+            return false
+        }
+        if node.Right != nil {
+            st = append(st, node.Right)
+        }
+        if node.Left != nil {
+            st = append(st, node.Left)
+        }
+    }
+    return true
+}
+
+func getDepth(cur *TreeNode) int {
+    st := make([]*TreeNode, 0)
+    if cur != nil {
+        st = append(st, cur)
+    }
+    depth := 0
+    result := 0
+    for len(st) > 0 {
+        node := st[len(st)-1]
+        if node != nil {
+            st = st[:len(st)-1]
+            st = append(st, node, nil)
+            depth++
+            if node.Right != nil {
+                st = append(st, node.Right)
+            }
+            if node.Left != nil {
+                st = append(st, node.Left)
+            }
+        } else {
+            st = st[:len(st)-1]
+            node = st[len(st)-1]
+            st = st[:len(st)-1]
+            depth--
+        }
+        if result < depth {
+            result = depth
+        }
+    }
+    return result
+}
+```
+
 ### JavaScript:
 
 递归法：