Tree_Graph determine whether to balance the binary tree @ CareerCup

ImplementafunctiontocheckifabinarytreeisbalancedForthepurposesofthisquestion, abalancedtreeisdefinedtobeatreesuchthattheheightsof

Implement a function to check if a binary tree is balanced. for the purposes of this question, a balanced tree is defined to be a tree such that the heights of the two subtrees of any node never differ by more than one.

A balanced binary tree is defined as an empty tree or its left and right subtrees. the absolute value of the height difference cannot exceed 1, and both left and right subtrees are a balanced binary tree.

Ideas:

1) first write a recursive tree height function, and then check whether the height difference of the subtree is greater than 1.

2) optimization: put the logic of checking whether the height difference of the subtree is greater than 1 in a recursive function that calculates the height of the tree, and return the result in time when an imbalance is encountered.

Note:

This question is different from asking whether a tree is balanced (the distance between any two leaf nodes of the tree and the root node is not greater than 1 ):

VcD4KPHA + PGJyPgo8L3A + Release/release/ydLUx/PK97XE1 + Release/release + 2yL/Jss6/release + CjwvcD4KPHA + Release/release + 2yKOsyLu687/JtcOhozwv CD4KPHA + ss6/fingerprint + PGJyPgo8L3A + CjxwPs/Cw + bKx8XQts/kx7fxxr1_rb + fill = "brush: java;"> package Tree_Graph; import CtCILibrary. assortedMethods; import CtCILibrary. treeNode; public class S4_1 {// recursive decision tree balance binary tree // Time: O (N ^ 2) public static boolean isBalanced (TreeNode root) {if (root = null) {return true;} int heightDiff = GetHeight (root. left)-getHeight (root. right); if (Math. abs (heightDiff)> 1) {// unbalanced return false;} else {return isBalanced (root. left) & isBalanced (root. right) ;}}// recursively retrieve the height of the tree public static int getHeight (TreeNode root) {if (root = null) {return 0 ;} return Math. max (getHeight (root. left), getHeight (root. right) + 1 ;} // ==================================== Improved version optimized version // put the logic for determining whether to balance in the checkHeight function, edge calculation height ,// Determines whether the edge is balanced. if it is not balanced,-1 // Time: O (N), Space: O (H), H: height of treepublic static boolean isBalanced2 (TreeNode root) is directly returned) {if (checkHeight (root) =-1) {return false;} else {return true ;}} // calculate the edge height and determine whether to balance public static int checkHeight (TreeNode root) {if (root = null) {return 0;} int leftHeight = checkHeight (root. left); if (leftHeight =-1) {return-1;} int rightHeight = checkHeight (root. right); if (rightHei Ght =-1) {return-1;} int heightDiff = leftHeight-rightHeight; if (Math. abs (heightDiff)> 1) {return-1;} return Math. max (leftHeight, rightHeight) + 1;} public static void main (String [] args) {// Create balanced treeint [] array = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; TreeNode root = TreeNode. createMinimalBST (array); System. out. println ("Root? "+ Root. data); System. out. println (" Is balanced? "+ IsBalanced (root); // cocould be balanced, actually, but it's very unlikely... treeNode unbalanced = new TreeNode (10); for (int I = 0; I <10; I ++) {unbalanced. insertInOrder (AssortedMethods. randomIntInRange (0,100);} System. out. println ("Root? "+ Unbalanced. data); System. out. println (" Is balanced? "+ IsBalanced (unbalanced ));}}