提交234,617,101题

Author: MistRay

leetcode/src/main/java/com/mistray/link/PalindromeLinkedList234.java

@@ -0,0 +1,67 @@
+package com.mistray.link;
+
+import java.util.ArrayList;
+
+/**
+ * @author ZJY(MistRay)
+ * @Project algorithm-study
+ * @Package com.mistray.link
+ * @create 2020年03月04日 15:02
+ * @Desc
+ */
+public class PalindromeLinkedList234 {
+
+
+    public static void main(String[] args) {
+        System.out.println(2%2);
+    }
+
+    // 双指针法
+    public boolean isPalindrome(ListNode head) {
+        if (head == null || head.next == null){
+            return true;
+        }
+        ArrayList<ListNode> list = new ArrayList<>();
+        ListNode fast = head;
+        ListNode slow = head;
+        int count = 1;
+        while (fast != null && fast.next != null) {
+            list.add(slow);
+            slow = slow.next;
+            fast = fast.next.next;
+            if (fast != null) {
+                count = count + 2;
+            } else {
+                count++;
+            }
+        }
+        ListNode tmp;
+        if (count % 2 == 0) {
+            tmp = slow;
+        } else {
+            tmp = slow.next.next;
+        }
+        for (int i = list.size() - 1; i > -1; i--) {
+            if (tmp.val != list.get(i).val) {
+                return false;
+            }
+            tmp = tmp.next;
+        }
+        return true;
+    }
+
+    // 复制数组双指针法
+    public boolean isPalindrome2(ListNode head) {
+        ArrayList<ListNode> list = new ArrayList<>();
+        while (head != null) {
+            list.add(head);
+            head = head.next;
+        }
+        for (int i = 0, f = list.size() - 1; i < list.size() / 2; i++, f--) {
+            if (list.get(i).val != list.get(f).val) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

leetcode/src/main/java/com/mistray/tree/MergeTwoBinaryTrees617.java

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+package com.mistray.tree;
+
+/**
+ * @author ZJY(MistRay)
+ * @Project algorithm-study
+ * @Package com.mistray.tree
+ * @create 2020年03月04日 9:59
+ * @Desc
+ */
+public class MergeTwoBinaryTrees617 {
+
+    public static void main(String[] args) {
+
+    }
+
+    public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {
+        if (t1 == null && t2 == null) {
+            return null;
+        } else if (t1 == null) {
+            return t2;
+        } else if (t2 == null) {
+            return t1;
+        } else {
+            t1.val = t1.val + t2.val;
+            t1.left = mergeTrees(t1.left, t2.left);
+            t1.right = mergeTrees(t1.right, t2.right);
+            return t1;
+        }
+    }
+}
+
+
+

leetcode/src/main/java/com/mistray/tree/SymmetricTree101.java

@@ -0,0 +1,29 @@
+package com.mistray.tree;
+
+/**
+ * @author ZJY(MistRay)
+ * @Project algorithm-study
+ * @Package com.mistray.tree
+ * @create 2020年03月04日 13:31
+ * @Desc
+ */
+public class SymmetricTree101 {
+
+    public static void main(String[] args) {
+
+    }
+
+    public boolean isSymmetric(TreeNode root) {
+       return helper(root,root);
+    }
+
+    public boolean helper(TreeNode t1, TreeNode t2) {
+        if ((t2 != null && t1 != null) && t1.val == t2.val) {
+            return helper(t1.right, t2.left) && helper(t1.left, t2.right);
+        } else if (t1 == null && t2 == null) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+}

leetcode/src/main/java/com/mistray/tree/TreeNode.java

@@ -0,0 +1,11 @@
+package com.mistray.tree;
+
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode(int x) {
+        val = x;
+    }
+}