solve problem Find Bottom Left Tree Value

Author: P-ppc

README.md

@@ -295,6 +295,7 @@ All solutions will be accepted!
 |34|[Find First And Last Position Of Element In Sorted Array](https://leetcode-cn.com/problems/find-first-and-last-position-of-element-in-sorted-array/description/)|[java/py/js](./algorithms/FindFirstAndLastPositionOfElementInSortedArray)|Medium|
 |75|[Sort Colors](https://leetcode-cn.com/problems/sort-colors/description/)|[java/py/js](./algorithms/SortColors)|Medium|
 |623|[Add One Row To Tree](https://leetcode-cn.com/problems/add-one-row-to-tree/description/)|[java/py/js](./algorithms/AddOneRowToTree)|Medium|
+|513|[Find Bottom Left Tree Value](https://leetcode-cn.com/problems/find-bottom-left-tree-value/description/)|[java/py/js](./algorithms/FindBottomLeftTreeValue)|Medium|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/FindBottomLeftTreeValue/README.md

@@ -0,0 +1,2 @@
+# Find Bottom Left Tree Value
+This problem is easy to solve by BFS

algorithms/FindBottomLeftTreeValue/Solution.java

@@ -0,0 +1,35 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public int findBottomLeftValue(TreeNode root) {
+        int val = -1;
+        LinkedList<TreeNode> stack = new LinkedList<TreeNode>(),
+                             nextStack = new LinkedList<TreeNode>();
+        
+        stack.add(root);
+        
+        while (stack.size() > 0) {
+            TreeNode node = stack.poll();
+            if (node.right != null)
+                nextStack.add(node.right);
+            if (node.left != null)
+                nextStack.add(node.left);
+            
+            
+            if (stack.size() == 0) {
+                val = node.val;
+                stack = nextStack;
+                nextStack = new LinkedList<TreeNode>();
+            }
+        }
+        
+        return val;
+    }
+}

algorithms/FindBottomLeftTreeValue/solution.js

@@ -0,0 +1,33 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var findBottomLeftValue = function(root) {
+    let val = -1,
+        stack = [ root ],
+        nextStack = []
+    
+    while (stack.length > 0) {
+        let node = stack.pop()
+        
+        if (node.right)
+            nextStack.unshift(node.right)
+        if (node.left)
+            nextStack.unshift(node.left)
+        
+        if (stack.length == 0) {
+            val = node.val
+            stack = nextStack
+            nextStack = []
+        }
+    }
+    
+    return val
+};

algorithms/FindBottomLeftTreeValue/solution.py

@@ -0,0 +1,30 @@
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def findBottomLeftValue(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        val = -1
+        stack = [root]
+        next_stack = []
+        
+        while len(stack) > 0:
+            node = stack.pop()
+            if node.right:
+                next_stack.insert(0, node.right)
+            if node.left:
+                next_stack.insert(0, node.left)
+            
+            if len(stack) == 0:
+                val = node.val
+                stack = next_stack
+                next_stack = []
+        
+        return val