Java solution 100 && 101

Author: gavinfish

java/_100SameTree.java

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+/**
+ * Given two binary trees, write a function to check if they are equal or not.
+ * Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
+ * <p>
+ * Created by drfish on 28/05/2017.
+ */
+public class _100SameTree {
+    public boolean isSameTree(TreeNode p, TreeNode q) {
+        if (p == null && q == null) {
+            return true;
+        }
+        if (p != null && q != null) {
+            if (p.val == q.val) {
+                return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+            }
+        }
+        return false;
+    }
+}

java/_101SymmetricTree.java

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+/**
+ * Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
+ * <p>
+ * For example, this binary tree [1,2,2,3,4,4,3] is symmetric:
+ *     1
+ *    / \
+ *   2   2
+ *  / \ / \
+ * 3  4 4  3
+ * But the following [1,2,2,null,3,null,3] is not:
+ *   1
+ *  / \
+ * 2   2
+ *  \   \
+ *  3    3
+ * <p>
+ * Note:
+ * Bonus points if you could solve it both recursively and iteratively.
+ * <p>
+ * Created by drfish on 28/05/2017.
+ */
+public class _101SymmetricTree {
+    public boolean isSymmetric(TreeNode root) {
+        if (root == null) {
+            return true;
+        }
+        return check(root.left, root.right);
+    }
+
+    private boolean check(TreeNode p, TreeNode q) {
+        if (p == null && q == null) {
+            return true;
+        }
+        if (p != null && q != null) {
+            if (p.val == q.val) {
+                return check(p.left, q.right) && check(p.right, q.left);
+            }
+        }
+        return false;
+    }
+}