update

Author: dingjikerbo

README.md

@@ -397,10 +397,12 @@
 |695|[Max Area of Island](https://leetcode.com/problems/max-area-of-island/)|[Java](leetcode/solution/src/MaxAreaOfIsland.java)|100||
 |703|[Kth Largest Element in a Stream](https://leetcode.com/problems/kth-largest-element-in-a-stream/)|[Java](leetcode/solution/src/KthLargestElementInAStream.java)|100||
 |771|[Jewels and Stones](https://leetcode.com/problems/jewels-and-stones/)|[Java](leetcode/solution/src/JewelsAndStones.java)|100||
+|814|[Binary Tree Pruning](https://leetcode.com/problems/binary-tree-pruning/)|[Java](leetcode/solution/src/JewelsAndStones.java)|80||
 |819|[Most Common Word](https://leetcode.com/problems/most-common-word/)|[Java](leetcode/solution/src/MostCommonWord.java)|85||
 |843|[Guess the Word](https://leetcode.com/problems/guess-the-word/)|[Java](leetcode/solution/src/GuessTheWord.java)|90||
 |844|[Backspace String Compare](https://leetcode.com/problems/backspace-string-compare/)|[Java](leetcode/solution/src/BackspaceStringCompare.java)|100||
 |849|[Maximize Distance to Closest Person](https://leetcode.com/problems/maximize-distance-to-closest-person/)|[Java](leetcode/solution/src/MaximizeDistanceToClosestPerson.java)|80||
 |857|[Minimum Cost to Hire K Workers](https://leetcode.com/problems/minimum-cost-to-hire-k-workers/)|[Java](leetcode/solution/src/MinimumCostToHireKWorkers.java)|70||
+|872|[Leaf-Similar Trees](https://leetcode.com/problems/leaf-similar-trees/)|[Java](leetcode/solution/src/LeafSimilarTrees.java)|80||
 |904|[Fruit Into Baskets](https://leetcode.com/problems/fruit-into-baskets/)|[Java](leetcode/solution/src/FruitIntoBaskets.java)|90||
 |929|[Unique Email Addresses](https://leetcode.com/problems/unique-email-addresses/)|[Java](leetcode/solution/src/UniqueEmailAddresses.java)|90||

leetcode/solution/src/BinaryTreePruning.java

@@ -0,0 +1,21 @@
+public class BinaryTreePruning {
+
+    public TreeNode pruneTree(TreeNode root) {
+        return helper(root) ? root : null;
+    }
+
+    private boolean helper(TreeNode root) {
+        if (root == null) {
+            return false;
+        }
+        boolean left = helper(root.left);
+        boolean right = helper(root.right);
+        if (!left) {
+            root.left = null;
+        }
+        if (!right) {
+            root.right = null;
+        }
+        return root.val == 1 || left || right;
+    }
+}

leetcode/solution/src/BinaryTreeTilt.java

@@ -2,6 +2,10 @@ public class BinaryTreeTilt {
 
     int tilt = 0;
 
+    /**
+     * 这题意思是遍历所有结点，对每个节点计算tilt，然后求和
+     * 对于给定root，其tilt为左子树所有节点的和与右子树所有结点的和的差的绝对值
+     */
     public int findTilt(TreeNode root) {
         helper(root);
         return tilt;

leetcode/solution/src/FindModeInBinarySearchTree.java

@@ -62,51 +62,4 @@ private void inorderTraverse(TreeNode root) {
 
         inorderTraverse(root.right);
     }
-
-
-    /**
-     * 如下是空间为O(l)的写法
-     */
-    int mCurVal;
-    int mMaxElemSize;
-    int idx;
-    int[] modes;
-
-    public int[] findMode2(TreeNode root) {
-        helper(root);
-        modes = new int[mMaxElemSize];
-        mCurCount = 0;
-        helper(root);
-        return modes;
-    }
-
-    private void helper(TreeNode node) {
-        if (node == null) {
-            return;
-        }
-
-        helper(node.left);
-
-        if (node.val == mCurVal) {
-            mCurCount++;
-        } else {
-            mCurCount = 1;
-            mCurVal = node.val;
-        }
-
-        if (modes == null) {
-            if (mCurCount == mMaxCount) {
-                mMaxElemSize++;
-            } else if (mCurCount > mMaxCount) {
-                mMaxElemSize = 1;
-                mMaxCount = mCurCount;
-            }
-        } else {
-            if (mCurCount == mMaxCount) {
-                modes[idx++] = mCurVal;
-            }
-        }
-
-        helper(node.right);
-    }
 }

leetcode/solution/src/InorderSuccessorInBST.java

@@ -35,7 +35,7 @@ public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
         if (root == null) {
             return null;
         }
-        if (root.val > p.val) {
+        if (p.val < root.val) {
             TreeNode node = inorderSuccessor(root.left, p);
             return node != null ? node : root;
         } else {
@@ -60,7 +60,7 @@ public TreeNode predecessor(TreeNode root, TreeNode p) {
     public TreeNode inorderSuccessor2(TreeNode root, TreeNode p) {
         TreeNode res = null;
         while (root != null) {
-            if (root.val > p.val) {
+            if (p.val < root.val) {
                 res = root;
                 root = root.left;
             } else {

leetcode/solution/src/LeafSimilarTrees.java

@@ -0,0 +1,53 @@
+import java.util.Stack;
+
+public class LeafSimilarTrees {
+
+    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
+        TreeIterator iterator1 = new TreeIterator(root1);
+        TreeIterator iterator2 = new TreeIterator(root2);
+
+        while (true) {
+            TreeNode node1 = iterator1.nextLeaf();
+            TreeNode node2 = iterator2.nextLeaf();
+
+            if (node1 == null && node2 == null) {
+                return true;
+            }
+            if (node1 == null || node2 == null) {
+                return false;
+            }
+            if (node1.val != node2.val) {
+                return false;
+            }
+        }
+    }
+
+    public class TreeIterator {
+        Stack<TreeNode> stack;
+        TreeNode root;
+
+        TreeIterator(TreeNode root) {
+            this.root = root;
+            stack = new Stack<>();
+        }
+
+        TreeNode nextLeaf() {
+            TreeNode ret;
+            while (!stack.isEmpty() || root != null) {
+                if (root != null) {
+                    stack.push(root);
+                    ret = root;
+                    root = root.left;
+
+                    if (ret.left == null && ret.right == null) {
+                        return ret;
+                    }
+
+                } else {
+                    root = stack.pop().right;
+                }
+            }
+            return null;
+        }
+    }
+}

leetcode/src/Main.java

@@ -6,21 +6,8 @@ public class Main {
 
     public static class Solution {
 
-        int tilt = 0;
+        public TreeNode pruneTree(TreeNode root) {
 
-        public int findTilt(TreeNode root) {
-            helper(root);
-            return tilt;
-        }
-
-        private int helper(TreeNode root) {
-            if (root == null) {
-                return 0;
-            }
-            int left = helper(root.left);
-            int right = helper(root.right);
-            tilt += Math.abs(left - right);
-            return left + right + root.val;
         }
     }