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leetcode/breadth-first-search/SymmetricTree.java
46 строк
1 KB
Kevin Naughton Jr
finish renaming files and directories
27 мар 2018, 19:52
27 мар 2018, 19:52
ec6dfb5
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// Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). // 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 /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class SymmetricTree { public boolean isSymmetric(TreeNode root) { if(root == null) { return true; } return helper(root.left, root.right); } public boolean helper(TreeNode left, TreeNode right) { if(left == null && right == null) { return true; } if(left == null || right == null || left.val != right.val) { return false; } return helper(left.right, right.left) && helper(left.left, right.right); } }